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EK-RK5JF-MM-001

May 1976

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Document:	RK05/RK05J/RK05F Disk Drive Maintenance Manual
Order Number:	EK-RK5JF-MM
Revision:	001
Pages:	135
Original Filename:

OCR Text

R K05/R K05J/R K05F
disk drive
maintenance manual

EK-RK5JF-MM-001

digital equipment corporation • maynard, massachusetts

1st Edition, November 1976

The material in this manual is for informational
purposes and is subject to change without notice.
Digital Equipment Corporation assumes no responsibility for any errors which may appear in this
manual.
Printed in U.s.A.

'TIm document was set on DIGITAL's DECset-8000
computerized typesetting system.

The following are trademarks of Digital Equipment
Corporation, Maynard, Massachusetts:
DEC
DECCOMM
DECsystem-IO
DECSYSTEM-20

DEC tape
DECUS
DIGITAL
MASS BUS

PDP
RSTS
TYPESET-8
TYPESET-II
UNIBUS

CONTENTS
Page
CHAPTER 1

GENERAL INFORMATION

1.1
1.2
1.3
1.4
1.5
1.5.1
1.5.2
1.5.3
1.5.4
1.5.5
1.5.6
1.5.7
1.5.8

INTRODUCTION
WARRANTY
SPECIFICATIONS
50/60 Hz POWER OPTION
MAJOR ASSEMBLIES AND SYSTEMS
Controls and Indicators
Spindle and Drive
Linear Positioner . . . . .
Cartridge-Handling System
Logic Assembly
Air System . . .
Power Supply
Read/Write Heads

CHAPTER 2

INSTALLATION

2.1
2.2
2.3
2.4
2.5
2.5.1
2.5.2
2.5.3
2.5.4

UNPACKING AND INSPECTION
............. .
MECHANICAL INSTALLATION AND CHECKOUT . . . . .
CARTRIDGE-HANDLING PRACTICES AND PRECAUTIONS
CARTRIDGE PACKING AND SHIPPING
NORMAL OPERATING PROCEDURES
RK05 and RK05-J Cartridge Loading
RK05 and RK05-J Cartridge Unloading
RK05-F Cartridge Installation
RK05-F Cartridge Removal
..... .

CHAPTER 3

INTERFACE

3.1

GENERAL
....... .
INPUT INTERFACE LINES
RK11-D . . . . . . .
Select (4 Lines)
Cylinder Address (8 Lines)
Strobe . . . . .
Head Select
Write Protect Set ..
Write Data and Clock
Write Gate
Restore (RTZ) .. .
Read Gate . . . . .
OUTPUT INTERFACE LINES
File Ready (Drive Ready)
Read, Write, or Seek Ready/On Cylinder
Address Accepted . . . . . . . . . . .
Address Invalid (Logic Address Interlock)

3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5

3.2.6
3.2.7

3.2.8
3.2.9
3.2.1 0
3.3.1
3.3.2
3.3.3
3.3.4

iii

1-1
1-1
1-1
1-4
1-4

1-4
1-4
1-10
1-10
1-13
1-13
1-13

1-13

2-1
2-3
2-7
2-8
2-8
2-8
2-8

2-9
2-10

3-1
3-1

3-3
3-3
3-3

3-3
3-3

3-3
3-3
3-4

3-4
3-4
3-4

3-4
3-4

CONTENTS (Cont)
Page
3.3.5
3.3.6
3.3.7
3.3.8
3.3.9
3.3.10
3.3.11
3.3.12
3.3.13
3.3.14
3.3.15

Seek Incomplete ..
Write Protect Status
Write Check
Read Data . . . . .
Read Clock . . . . .
Sector Address (4 Lines)
Sector Pulse
Index Pulse
ACLOW
DC LOW
High Density /RK05 L

3-4
3-4
3-4

3-5
3-5
3-5
3-5
3-5
3-5
3-5
3-5

CHAPTER 4

THEORY OF OPERATION

4.1
4.1.1
4.1.2
4.1.3
4.1.4
4.2
4.2.1
4.2.2
4.2.3
4.2.3.1
4.2.3.2
4.2.3.3
4.2.3.4
4.2.4
4.2.4.1
4.2.4.2
4.2.5
4.2.5.1
4.2.5.2
4.2.5.3
4.2.5.4
4.2.6
4.3
4.3.1
4.3.1.1
4.3.1.2
4.3.2
4.3.2.1
4.3.2.2
4.3.2.3

FUNCTIONAL DESCRIPTION
Start . . . . . . . . . . .
Stop . . . . . . . . . . . .
Track Addressing and Head Positioning
Recording Technique
LOGICAL DESCRIPTION . . . . .
Power ON/OFF Sequence
Start
Stop . . . . . . . .
Normal Stop
Low Speed Stop
AC Low Stop
DC Low Stop ..
Disk Drive Addressing
RK11-D Address Selection
RKI1-C or RK8/E Address Selection
Seek . . . . . . . . .
Load Heads Seek
Forward Seek . .
Reverse Seek
Return-to-Zero (Restore) Seek
Sector/Index Pulse Generation
CARRIAGE POSITIONING . . .
Positioner Servo Description
Velocity Mode
Detent Mode . . . . .
Servo Circuit Description
Linear Positioner Transducer
Velocity Function Generator
Velocity Synthesizer

4-1
4-1
4-1
4-5
4-5
4-S
4-S
4-5
· 4-11
· 4-11
· 4-12
· 4-12
4-12
· 4-12
· 4-12
· 4-12
· 4-13
· 4-13
· 4-13
· 4-15
· 4-15
· 4-16
· 4-16
· 4-16
· 4-18
· 4-19
· 4-19
· 4-19
.. 4-19
· 4-19

CONTENTS (Cont)

Page
4.4
4.4.1
4.4.2
4.5
4.5.1
4.5.2
4.6

READ/WRITE
Read Operation
Write Operation
FAULT DETECTION
Current Fault
Positioner Lamp Fault
POWER SUPPLY DESCRIPTION

CHAPTERS

MAINTENANCE

5.1
5.1.1
5.1.2
5.2
5.3
5.3.1
5.3.1.1
5.3.1.2
5.3.2
5.3.2.1
5.3.2.2
5.3.2.3
5.3.2.4
5.3.2.5
5.3.2.6
5.3.3
5.3.3.1
5.3.3.2
5.3.3.3
5.3.4
5.3.4.1
5.3.4.2
5.3.4.3
5.3.5
5.3.5.1
5.3.5.2
5.3.5.3
5.3.6
5.3.6.1
5.3.6.2
5.3.7
5.3.8
5.3.8.1
5.3.8.2
5.4
5.4.1

CUSTOMER EQUIPMENT CARE
Weekly Care . . . . . . . . .
Monthly Care
........ .
PREVENTIVE MAINTENANCE . . . . .
CORRECTIVE MAINTENANCE
Linear Positioner . . . . . . .
Positioner Removal ..
Positioner Replacement
Carriage
........ .
Carriage Removal .. .
Carriage Replacement .
Carriage Bearing Assembly Removal
Carriage Bearing Assembly Replacement
Transducer Block Removal and Replacement
Transducer Bulb Replacement
Read/Write Heads
Carriage Revisions
Head Removal
Head Replacement
Spindle . . . . . . . . . .
Spindle Removal
Spindle Replacement
Spindle Ground (Carbon Brush) Removal and Replacement
Spindle Drive Motor
Motor Removal . . . . . . . . . . .
Motor Replacement . . . . . . . . .
Drive Belt Removal and Replacement
Blower Motor
..... .
Blower Removal
Blower Replacement
Power Supply Removal
Cartridge Cleaning
Cartridge Cleaning Procedure
Adverse Disk Conditions
ALIGNMENT, CHECKS, AND ADJUSTMENTS
Alignment Cartridges . . . . . . . . . . . .

· 4-22
· . 4-22
· 4-26
· 4-27
· 4-27
· 4-27
· 4-27

5-1
5-1
5-1
5-1
5-3
5-3
5-3
5-4
5-6
5-6
5-7
5-8
5-9
5-9
· 5-10
. . . 5-10
· . 5-10
5-10
5-10
· . 5-13
5-13
5-14
· 5-15
· 5-15
5-15
· . 5-16
· 5-17
5-17
· 5-17
5-19
5-19
· 5-19
· 5-19
· 5-21
· 5-22
· 5-22

CONTENTS (Cont)
Page
5.4.l.1
5.4.l.2
5.4.2
5.4.2.l
5.4.2.2
5.4.3
5.4.4
5.4.4.1
5.4.4.2
5.4.5
5.4.5.l
5.4.5.2
5.4.6
5.5
5.6
5.6.1
5.6.2
5.6.3
5.6.4

RK05K-AC Alignment Cartridge
2315 CE Test Cartridge Shim Installation
Servo System Timing Checks and Adjustments
Dynamic Off-Line Checks and Adjustments
Static Tests and Adjustments . . . . . . .
Read/Write Data Separator (G 180 Card) Adjustment
Read/Write Head Check and Alignment
RK05K -AC Alignment Cartridge
2315 CE Pack . . . . . . . . . .
Index/Sector Timing Adjustment
RK05K-AC Alignment Cartridge
2315 CE Pack . . . . .
Cartridge Receiver Alignment
SPARE PARTS
TROUBLESHOOTING
Power Supply
Controls and Indicators
Mechanical Checks
Electronic Checks

5-22
5-23
5-25
5-26
5-34
5-35
5-36
5-36
5-44
5-50
5-50
5-52
5-55
5-59
5-60
5-60
5-62
5-62
5-64

ILLUSTRATIONS
Figure No.

1-1
1-2
1-3
1-4
1-5
1-6
1-7
1-8
1-9
1-10
1-11
1-12
2-1
2-2
2-3
2-4
2-5
2-6
3-1
/L 1
,-_c

Title

Page

Location of Major Assemblies and Systems (RK05)
Location of Major Assemblies and Systems (RK05-J)
Location of Major Assemblies and Systems (RK05-F)
Controls and Indicators . . . . . . . . . .
Spindle and Drive System . . . . . . . . .
Linear Positioner (RK05/RK05-J/RK05-F)
RK05 Cartridge-Handling System .
RK05-J Cartridge-Handling System
RK05-F Cartridge-Handling System
Air System
........... .
Head Loading . . . . . . . . . . .
Relationship of Disk Head, Disk, and Contaminants
Shipping Bracket and Shipping Strap Locations
RKII-C or RKII-D Interface Cable Installation
Chassis Slide Mounting
..... .
RK8/E Interface Cable Installation
RK05-F Cartridge . . . . . . . . .
RK05-F Cartridge Instal1ed
Controller/RKOS Disk Drive Interface Lines and Pin Assignments
Flll1ctiollal Bl()ck Di:agra!11

1-5
1-6
1-7
1-8
1-10
1-11
1-12
1-14
1-15
1-16
1-16
1-17
2-2
2-3
2-4
2-6
2-9
2-10
3-2

ILLUSTRATIONS (Cont)
Figure No.
4-2
4-3

4-4
4-5
4-6
4-7
4-8
4-9
4-10
4-11
4-12
4-13
4-14
4-15
4-16
4-17
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
5-9
5-10
5-11
5-12
5-13
5-14
5-15
5-16
5-17
5-18
5-19
5-20
5-21
5-22
5-23
5-24
5-25
5-26
5-27
5-28
5-29

Title
Start Flowchart
Stop Flowchart
Seek Flowchart
Return-to-Zero (Restore) Flowchart
Read/Write Head
......... .
Simplified Read/Write Head Circuit
Double Frequency Pulse Relationship
Control and Interlock Block Diagram
Sector/Index Timing
Servo System Block Diagram
Linear Positioner Transducer
Simplified Positioner Servo Logic
Velocity Profile (RK05/RK05-J)
Simplified Data Separator Circuit
Read Waveforms . . . . . . . . .
Internal Power Supply Connections
Prefilter . . . . . . . . . . . . . . .
Absolute Filter Removal
Top View of RK05 with Cover Removed
Carriage Bearing Assembly Removal
Read/Write Head Carriage Revision
Read/Write Head Replacement
Spindle Replacement
Drive Belt . . . . . . . . .
Carbon Brush Replacement
Blower Motor Removal
How to Read a Vernier
Negligible Runout . . . .
Considerable Runout
CE Test Cartridge Shim Installation
Sine Amplitude/Offset and Velocity Offset Waveform
Cosine Amplitude/Offset Waveform
Velocity Amplitude Waveform
Acceleration Waveform
Full Stroke Waveform . . . .
Full Stroke Position Waveform

Outer LLfTIit Waveform
RK05K-AC Head Alignment Waveforms
Read/Write Head Adjustments
2315 CE Pack Head Alignment Waveforms
Index/Sector Waveform . . . . .
Cartridge-to-Receiver Clearance . . . . . .
Cartridge Receiver Clearances . . . . . . . .
Cartridge Receiver, Newer Models (RK05/RK05-J)
Cartridge Receiver, RK05-F . . . . . . . . . . . .

vii

Page
4-3
4-4
4-6
4-7
4-8
4-8
4-9
4-10
· 4-17
4-18
· 4-20
· 4-21
· 4-22
4-23
. . . . . 4-24
. . . . .
4-28
. . . .. 5-2
5-5
5-6
5-8
· 5-11
5-12
· 5-14
· 5-15
· 5-16
. . . . 5-18
· 5-22
. . . . . . 5-24
5-24
· . 5-25
· . 5-29
5-30
5-31
· 5-32
5-33
· 5-33
5-34
· 5-37
5-41
· 5-45
5-52
5-56
5-57
· . 5-58
· . 5-58

ILLUSTRATIONS (Cont)
Figure No.
5-30
5-31
5-32

Title
Troubleshooting Flowchart
Door Locking Bar Location
Cartridge Seating Elements

Page
5-61
5-63
5-63

TABLES
Table No.
1-1
1-2
5-1
5-2
5-3
5-4

Title
Performance Specifications
. . . . . . . . . . . . .
Controls and Indicators for the RK05, RK05-J, and RK05-F
Recommended Tools and Test Equipment
Positioner Transducer Wire Configuration
Servo System Checks
Servo System Adjustments
...... .

viii

Page
1-2
1-8
5-3
5-4
5-26
5-30

CHAPTER 1
GENERAL INFORMATION

1.1 INTRODUCTION
The RK05, RK05-J, and RK05-F Disk Drives, which comprise the RK05 family of disk drives, are
self-contained, random-access, data storage devices that are especially well suited for small or mediumsized computer systems, data acquisition systems, terminals, and other storage applications. Operational power for all of these devices is provided by power supplies located within the drive cabinets.
Drives in the RK05 family are available in four models, each of which operates on a different power
line.
These compact, lightweight drives use high-density, single-disk, 12- or 16-sector cartridges as the storage medium. The cartridge used in the RK05 and RK05-J Disk Drives is removable; the cartridge used
in the RK05-F is fixed. Two movable heads, one flying above the rotating disk surface and one below,
can read or record up to 406 data tracks in the RK05 and RK05-J models, and up to 812 data tracks in
the RK05-F. In all drives, the disks revolve at 1500 rpm. The double-frequency, nonreturn-to-zero
(NRZ) recording method used in these drives can store up to 2~ million bits of on-line data in the
RK05 and RK05-J, and up to 5.0 million bits in the RK05-F. Data formatting is governed entirely by
the operating system.
With the address select logic contained in each drive, up to eight RK05 or RK05-J Disk Drives
(depending on the type of system) can be "daisy-chained" and operated from a single controller bus.
The RK05-F is addressed as two logical RK05-Js. Combinations ofRK05, RK05-J, and RK05-F Disk
Drives are possible, as long as the RK05-F drives are addressed as "Drives 0/1," "Drives
2/3,""Drives 4/5," or "Drives 6/7." No other addressing number pairs may be used to address an
RK05-F.

1.2 WARRANTY
"Removable media involve use, handling and maintenance which are beyond DEC's direct control.
DEC disclaims responsibility for performance of the Equipment when operated with media not meeting DEC specifications or with media not maintained in accordance with procedures approved by
DEC. DEC shall not be liable for damages to the Equipment or to media resulting from such
operation."
1.3 SPECIFICATIONS
Table 1-1 lists the performance specifications for the RK05 family of disk drives. Where applicable,
distinctions are made between RK05, RK05-J, and RK05-F Disk Drives and 12- and 16-sector
cartridges.

1-1

Table 1-1 Performance Specifications
Characteristic

Specification

Storage Medium
Type

Single disk magnetic cartridge (RK05, RK05J removable; RK05F - nonremovable)
14 inches

Disk Diameter
Magnetic Heads
Number

Two

Recording Density and Format
Density
Tracks (RK05 and RK05J)
Tracks (RK05F)
Cylinders (RK05 and RK05J)
Cylinders (RK05F)
Sectors (records)(RK05 and RK05J)

2200 bpi max.
406 (200 plus 3 spares on each side of the disk)
812 (400 plus 6 spares on each side of the disk)
203 (two tracks each)
406 (two tracks each)
4872 (12 per revolution)
6496 (16 per revolution)
9744 (12 per revolution)
12996 (16 per revolution)

Sectors (records)(RK05F)
Bit Capacities (unfonnatted)*
Per Disk (RK05 and RK05J)
Per Disk (RK05F)
Per Inch
Per Cylinder
Per Track
Per Sector

25 million
50 million
2040 (max. at inner track)
115,200
57,600
4,800/3,844

Access Times
Disk Rotation
Average Latency
Head Positioning
(including settling time)

}
1500 ± 30 rpm
20 ms (half rotation)
RK05/RK05J
-for adjacent tracks
0 ms
-average
50 ms
-for 200 track movement 85 ms

Bit Transfer*
Transfer Code
Transfer Rate

Double frequency, NRZ recording
1.44M bits per seconds

Electrical Requirements
Voltage
Power
Starting Current

115/230 Vac @ 50/60 Hz ± .05 Hz
250 VA
Power only: 1.8 A
Start spindle: 10 A (for 2 seconds)

*Some RKll·D systems record at 1.54 bits/second which increases the bit density and capacity accordingly.

1-2

Table 1-1 Performance Specifications (Cont)

Specification

Characteristic
Model Designation
RK05-AA, RK05J-AA, RK05F-AA, RK05F-FA
RK05-AB, RK05J-AB, RK05F-AB, RK05F-FB
RK05-BA, RK05J-BA, RK05F-AC, RK05F-FC
RK05-BB, RK05J-BB, RK05F-AD, RK05F-FD
Environment
Ambient Temperature
Relative Humidity
Barometric Pressure
Temperature, Change Rate
Temperature, Interchangeable Range
(RK05, RK05J)

95 -130 Vac@ 60 ± 0.5 Hz
190 - 260 Vac @ 60 ± 0.5 Hz
95 - 130 Vac@ 50 ± 0.5 Hz
190 - 260 Vac @ 50 ± 0.5 Hz

50° - 110° F (10° - 43° C nominal)
8% - 80% (no condensation)
10,000 ft (3,000 meters) max.
10° F (6° C) per hr
30° F (17° C)

Dimensions and Weight
Width
Depth
Height
Weight

19 inches (48 cm)
26-1/2 inches (67 cm)
10-1/2 inches (27 cm)
110lb (50 kg)

1-3

1.4 50/60 Hz POWER OPTION
Disk drives in the RK05 family are available in. the following four power models:
RK05-AA
RK05-J-AA
RK05-F-AA

}

95 - 130 Vac @ 60 Hz

RK05-AB
RK05-J-AB
RK05-F-AB

}

190 - 260 Vac @ 60 Hz

RK05-BA
RK05-J-BA
RK05-F-BA

}
}

RK05-BB
RK05-J-BB
RK05-F-BB

95 - 130 Vac @ 50 Hz

190 - 260 Vac @ 50 Hz

Changing from 50 to 60 Hz operation requires a different spindle drive pulley, and the motor must be
moved as described in Paragraph 5.3.5 of this manual. Changing from 115 V to 230 V operation
requires that the power connector (P2) be reconfigured (Paragraph 4.6).

1.5 MAJOR ASSEMBLIES AND SYSTEMS
The drives in the RK05 family are composed of the following major assemblies and systems:
Controls and Indicators
Spindle and Drive System
Linear Positioner
Cartridge Handling System
Logic Assembly
Air System
Power Supply
Read/Write Heads
Figures 1-1, 1-2, and 1-3 illustrate the locations; subsequent paragraphs describe the functions of each
of the major assemblies and systems.

1.5.1 Controls and Indicators
The controls and indicators (Figure 1-4) required for normal operation are located on the front of the
drive cabinet. Table 1-2 describes the function of each control or indicator.
1.5.2 Spindle and Drive
The spindle and drive system (Figure 1-5) comprises the spindle, spindle drive motor, and the recording disk. A 50/60 Hz, split-phase ac motor transfers torque (via the drive belt) to the spindle drive
pulley. Belt tension is maintained by a tension spring anchored to the baseplate.
The spindle speed is electronically tested by a circuit that measures the INDEX PULSE interval. When
the interval increases to approximately 45 ms, indicating an unsafe speed, the drive is cycled down. If
the RUN/LOAD switch is placed in the LOAD position. ac power is removed from the motor, and the
spindle coasts to a halt.

1-4

POWER-FAIL
HEAD-RETRACTING
BATTERIES

LINEAR POSITIONER

LOGIC ASSEMBLY

POWER SUPPLY

READ/WRITE

ABSOLUTE
AIR FILLER
(UNDERNEATH
UNIT)

DRIVE MOTOR

CARTRIDGE
CONE

SECTOR
TRANSDUCER

CARTRIDGE
SUPPORT POSTS
6858-6

Figure 1-1

Location of Major Assemblies and Systems (RK05)

1-5

POWER-FAIL
HEAD-RETRACTING
BATTERIES

POWER
SUPPLY

BLOWER

DUCKBILL
~--

READ/WRITE
HEADS

ABSOLUTE
AIR FILTER - (UNDERNEATH
UNIT)

............ -

~rll"ULC

DRIVE MOTOR
CARTRIDGE
AIR DUCT

CARTRIDGE
RECIEVER

CARTRIDGE
SUPPORT POSTS

Figure 1-2

Location of Major Assemblies and Systems (RK05-J)

1-6

7553-6

POWER-FAIL
HEAD-RETRACTING
BATTERIES

LINEAR POSITIONER

LOG IC ASSEMBLY

POWER SUPPLY - - - - - '

----BLOWER

DUCKBILL

READ/WRITE
HEADS

ABSOLUTE
AIR FILTER
(UNDERNEATH
UNIT)

SPINDLE

SPINDLE
DRIVE MOTOR

CARTRIDGE
AIR DUCT

SECTOR
TRANSDUCER

CARTRIDGE
SUPPORT POSTS

Figure 1-3

Location of Major Assemblies and Systems (RK05-F)

1-7

Figure 1-4 Controls and Indicators

Table 1-2 Controls and Indicators for the RK05, RKOS-J, and RK05-F
Controls and
Indicators
RUN/LOAD
(rocker switch)

Description
Placing this switch in the RUN position (provided that all interlocks are safe):
1.

locks the drive front door

accelerates the disk to operating speed

loads the read/write heads

lights the RDY indicator.

Placing this switch in the LOAD position:
1.

unloads the read/write heads

stops the disk rotation

unlocks the drive front door when the disk has stopped

lights the LOAD indicator.
CAUTION
Do not switch to the LOAD position during a write
operation; this results in erroneous data being recorded.

WTPROT
(rocker switch
spring-loaded off)

Placing this momentary contact switch in the WT PROT position lights the
WT PROT indicator and prevents a write operation; it also turns off the
FAULT indicator, if that is lit.
Depressing this switch in the WT PROT position a second time turns off the
WT PROT indicator and allows a write operation.

1-8

Table 1-2 Controls and Indicators for the RK05, RK05-J, and RK05-F (Cont)
Controls and
Indicators

Description

PWR
(indicator)

Lights when operating power is present. Goes off when operating power is
removed.

RDY
(indicator)

Lights when:
I.

the disk is rotating at the correct operating speed.

the heads are loaded.

no other conditions are present (all interlocks safe) to prevent a
seek, read, or write operation.

Goes off when the RUN/LOAD switch is set to LOAD.
ONCYL
(indicator)

Lights when:
1.

the drive is in the Ready condition.

a seek or restore operation is not being performed.

the read/write heads are positioned and settled.

Goes off during a seek or restore operation.
FAULT
(indicator)

Lights when:
1.

erase or write current is present without a WRITE GATE.

the linear positioner transducer lamp is inoperative.

Goes off when the WT PROT switch is pressed, or when the drive is recycled
through a RUN/LOAD sequence.
WTPROT
(indicator)

Lights when:
1.

the WT PROT switch is pressed.

the operating system sends a Write Protect command.

Goes off when the WT PROT switch is pressed a second time, or when the
drive is recycled through a RUN/LOAD sequence.
LOAD
(indicator)

Lights when the read/write heads are fully retracted and the spindle has
stopped rotating.

WT
(indicator)

Lights when a write operation occurs. Goes off when the write operation
terminates.

RD
(indicator)

Lights when a read operation occurs. Goes off when the read operation
terminates.
1-9

TENSION SPRING

DRIVE BELT

SPINDLE PULLEY

DRIVE MOTOR

Figure 1-5

Spindle and Drive System

1.5.3 Linear Positioner
The linear positioner (Figures 1-1, 1-2, or 1-3) consists of the linear motor, the carriage, the read/write
heads, and the linear positioner transducer. To move the read/write heads across the recording disk,
dc current is applied to the bobbin-wound armature (Figure 1-6) of the linear motor. The resulting
magnetic field reacts with a permanent magnet in the motor housing to either pull the armature into or
force it out of the permanent magnetic field, depending upon the polarity of the current applied to the
armature. This motion is transferred to the carriage, which is fastened to the armature. As a result, the
read/write heads, which are attached to the carriage, move across the surface of the disk.
Any carriage movement is detected by the linear positioner transducer, which is located on the underside of the carriage. The transducer output is used with the control logic to determined the cylinder
position of the heads, and in the servo logic to govern the speed of carriage travel.

1.5.4 Cartridge-Handling System
Cartridge handling differences exist among the RK05 family drives. The RK05 Disk Drive cartridge
system (Figure 1-7 a) consists of a cartridge receiver, two receiver lifting cams, an access door opener, a
duckbill, and two cartridge-support posts. During normal operation, the plastic cartridge is located
only by the duckbill and support posts. The cartridge merely guides the cartridge into position to be
picked up by the duckbill and support posts, allowing the recording disk to rotate freely on the spindle.
The rotating spindle drives the disk by magnetic coupling at the disk hub.
As the drive front door is opened, the lifting cams rotate to elevate the receiver to a slanted position,
and the magnetic coupling at the disk hub is released. When the disk cartridge is inserted into the
receiver (Figure 1-7b), the access door opener makes contact with and opens the access door in the rear
of the top cover, permitting entry of the read/write heads.
1-10

TRACK POSITION
SCALE

LINEAR TRANSDUCER
(UNDER CARRIAGE)

HEAD ADJUSTMENT
SCREWS

LOWER HEAD
CLAMP SCREW

UPPER HEAD
CLAMP SCREW

MOTOR HOUSING
ARMATURE
(PERMANENT MAGNET INSIDE)

CARRIAGE

CARRIAGE SLIDE

DUCKBILL
6858-5

(a) Older Style

HEAD ADJUSTMENT
SCREWS

LOWER HEAD
CLAMP SCREW

UPPER HEAD
CLAMP SCREW

(b) New Style
Figure 1-6

Linear Positioner (RK05/RK05-J /RK05-F)
1-11

MOTOR

(a) Cartridge Removed

(b) Cartridge Inserted
Figure 1-7

RK05 Cartridge-Handling System

1-12

As the drive front door is closed, the cartridge is lowered to the operating position and the magnetic
coupling again engages the disk hub. When the cartridge is in the operating position, the plastic case
depresses the cartridge-on switch and removes the no-cartridge interlock condition. The cartridge
receiver should not hold the cartridge tightly.
The RK05-J cartridge-handling system (Figure 1-8) is generally similar to that of the RK05, with the
exception that two cartridge clamps have been added to provide a positive cartridge location force. As
the drive front door is opened, the lifting cams rotate to elevate the cartridge receiver, and to lift the
cartridge clamps away from the cartridge, thus freeing the cartridge for removal. As the door is closed,
the receiver is lowered, and the cartridge clamps are simultaneously brought down on the upper surface of the cartridge to ensure proper cartridge seating on the cartridge support posts. In all other
functional aspects, the RK05 and RK05-J cartridge-handling systems are similar.
Because the RK05-F has a fixed cartridge, its cartridge-locating system is considerably simpler, consisting of a duckbill, a door-opening wedge, two cartridge-support posts, two cartridge-retaining
springs, and a cartridge-guide bracket. When the drive is prepared for initial operation at the customer's site, the retaining springs are attached (Figure 1-9b) to the front of the cartridge and the cartridge
door-opening wedge is inserted. The cartridge is then guided through the front of the drive and into
position on the duckbill by the cartridge-guide bracket and the cartridge-support posts, and secured
with the cartridge-retaining springs (Figure 1-9b).

1.5.5 Logic Assembly
The logic assembly (Figures 1-1, 1-2, and 1-3), in the right-rear portion of the disk drive, holds eight
printed circuit cards. Three of these cards contain the system logic and the read/write circuits. Two
cards contain the positioner servo logic. One card is the cable connector that interfaces the electronics
with the positioner and other chassis-mounted components. The remaining two cards contain the
interface cables and terminators.
1.5.6 Air System
The air system (Figure 1-10) consists of the prefilter, blower, cooling duct, inlet port, absolute filter,
outlet port, and air duct. As the blower rotates, unfiltered air is drawn through the prefilter, where it is
purged of large particles. The prefiltered air is then drawn across the logic assembly and through the
blower. Upon leaving the blower, approximately 30 percent of the air is channeled through the cooling
duct and directed onto the power supply. The remaining air from the blower is fed via the inlet port
into the absolute filter, where minute contamination is removed. The cleaned air is then taken to the
disk cartridge air door via the filter outlet port and the air duct. After passing through the disk
cartridge, the air circulates across the linear positioner and baseplate; it then exits the drive through
exhaust louvers in the front panel and in the chassis side next to the power supply.
1.5.7 Power Supply
The power supply (Figures 1-1, 1-2, and 1-3), in the left-rear portion of the disk drive, furnishes all dc
voltages for the drive. The power supply can operate with a 115 or 230 Vac, 50 or 60 Hz line voltage
input (Paragraph 4.6).
1.5.8 Read/Write Heads
Disk drives in the RK05 family contain two ramp-loaded read/write heads. One head functions on the
top surface of the recording disk, and the other one functions on the bottom surface. The heads are
mounted on suspension arms that rest, when the heads are unloaded, on a plastic cam block of the
nllckhi11
r::lntl1pvPT -r----o~nTln(J~ ronnprt
~11~npn~10n -----::lTm~ to
he::ln-Sollnnort
---------- {Fl(JllTP
,- -0--- 1-11'\
- - - f ' -F1M
- - - __
--------- thp
__ ---r--------- thp
---- ----- - r r - - - t::lil----A

_____

•

pieces. When the drive is placed in RUN mode, the positioner moves the heads forward toward cylinder zero. When the entire head slider pad has passed the edge of the disk, a ramp on the suspension
arm slides down the edge of the plastic cam block, thereby moving (loading) the heads close to the disk
surface. When loaded, the heads "fly" 80 to 100 microinches from the disk surface (Figure 1-12).

1-13

(a) Cartridge Removed

(b) Cartridge Inserted
Figure 1-8

RK05-j Cartridge-Handling Systern

1-14

7854-6

(a) Cartridge Removed
DOOR-OPENI NG

SPRINGS ATTACHED TO
FRONT OF CARTRIDGE
TO HOLD IN PLACE

(b) Cartridge Inserted
Figure 1-9

RK05-F Cartridge-Handling System

1-15

ELECTRONIC
MODULE
HOUSING
PREFILTER

AIR FLOW!NG
THRU PIS REGULATORS

CARTRIDGE
AIR DUCT

C;:>-0272

Figure 1-10 Air System

~ HEAD BRACKET

HEAD

____{-___!_

a SLIDER _CC:=--~:.
___

: : : : : :__ //7$/#~ff//J

• - - - -s -------fj-~~-r-(..,..t.~:-'I'~-"';;::;""---"'-:::~~"""'~--'_"'---"'"__

PAD (UNLOADED)

HEAD a SLIDER
PAD (LOADED)

DOWN (UPPER) HEAD
,....

- - -

HEAD
LOADING
' - - - - - - . . - : - - SPRING

RAMPS(

~_ :-=-:~: ,~~

___, - :-.::-~

,~::.:~.::::.::.::::;...--

Figure 1-11

UP (LOWER) HEAD

Head Loading

1-16

PLAs:~t-\-::-:_----~-L:-C-K-S
- .... -

CP-0254

)'5/ll7lMJ / /
58 MILES PER HOUR

08-0884

Figure 1-12

Relationship of Disk Head, Disk, and Contaminants

A film of air (air bearing) between the disk and the head acts as a force away from the disk, while the
cantilever spring is a counterbalancing force toward the disk. Thus, as long as the disk rotation
remains constant, the heads remain at a relatively constant distance away from the disk surface.
The Down (upper) Head is so-called by convention throughout the computer industry because it faces
down; the Up (lower) Head faces up. These designations were created to describe heads loaded onto a
multisurface (10 or 20) cartridge.
.
The recording device (read/write head) is a coil-wound ferrite core with an air gap. As current flows
through the coil, the induced flux magnetizes the surface of the disk passing under the gap. During a
write operation, when the current direction in the coil is reversed, a flux reversal is recorded on the
disk. During a read operation, the previously-recorded flux pattern on the disk induces current in the
head. Any flux reversal on the recording surface produces a pulse.

1-17

CHAPTER 2
INSTALLATION

2.1 UNPACKING AND INSPECTION
An RKOS, RKOS-J, or RKOS-F Disk Drive can be shipped in a rack as an integral part of a system or
in a separate container. If the drive is shipped in a rack, the rack should be positioned in the final
installation location and unpacked as follows:
1.

Remove the cabinet shipping brackets from the drive by removing the snap-on bezel beneath
the lowest drive.

Remove the screws attaching the shipping bracket and latch molding to both sides of the
drive. The drive may now be extended on the chassis slides.
CAUTION
Do not use the front door handle of the RK05 or
RK05-J to pull the drive out from the rack.

Slide the drive out about 3 inches from the rack and pull the shipping brackets out from the
sides of the drive. Replace the latch molding and the shipping bracket screws.

4. Slide the lowest drive out far enough to gain access to the shipping brackets on the drive
directly above it, and remove the screws from these two shipping brackets.
S.

Repeat Steps 3 and 4 for each drive in the rack.

Remove the drive bottom cover and remove the screws that attach the three internal shipping brackets to the baseplate (Figure 2-1a). (A 3/16-inch Allen wrench is required.)
CAUTION
Do not operate drive with shipping brackets attached.

7. If drives in the RKOS family are "daisy-chained" with RK03 drives in a multidrive installation, arrange the RKOSs consecutively at the controller end of the bus to avoid interruption
of the AC LOW and DC LOW interface lines, which are not carried by the RK03s. If this
arrangement is not possible, all RK05s that are separated on the bus by RK03s must be
connected by separate cables between their J06 connections (Figure 2-2).
8.

Remove the drive top cover and fel110Ve the nlounting screw and shipping strap from the
linear positioner (Figure 2-1 b). Turn the shipping strap upward and replace it on the linear
positioner, making sure that it is tightly secured.

2-1

SHIPPING BRACKETS

(a) Shipping Brackets

SHIPPING
STRAP

LINEAR
POSITIONER

MOUNTING
SCREW

(b) Shipping Strap on Linear Positioner
Figure 2-1

Shipping Bracket and Shipping Strap Locations

2-2

J06

INTERFACE CABLE

Figure 2-2

RKII-C or RKll-D Interface Cable Installation

Retain all packing material for possible reshipment. Inspect the drive for possible damage.
Report any damage to the carrier and to Digital Equipment Corporation.

10. In the case of RK05 family drive relocation reshipment, replace the shipping brackets and
shipping strap in the shipping position; repeat this unpacking and inspection procedure
when the drive is reinstalled.

If the drive is shipped in a separate container, use care while unpacking it. Do not drop the drive or
subject it to unreasonable impact.
2.2 MECHANICAL INSTALLATION AND CHECKOUT
If the RK05-type drive is to be installed in an existing rack, the chassis slides should first be installed in
the rack (Figure 2-3). The disk drive should be mounted on the chassis slides as follows: (If necessary,
refer to the RK05 Option Configuration Dwg. No. D-OC-RK05-0-15 for detailed mechanical specifications of a multidrive installation.)
1. Install cabinet stabilizers before mounting the drive, unless the weight of the rack is sufficient to prevent tipping when the drive is fully extended.
2. Pull the chassis slides out until they lock in the extended position.
3. Slide the drive onto the chassis slides until it locks~
4.

Remove the drive bottom cover and remove the screws that attach the three internal shipping brackets to the baseplate (Figure 2-1a).

2-3

r -

RACK

~-I

tt=--

---;-I

--~

_iJ

!-+r-- R.H. RAIL

L.H. RAIL-+

RK05

7.22

10.44

! t
f

1.75

1.47

DOD.
DODD

If!.
'il

CHASSIS
SLIDE

42.22
+

DOD.
DODD

+
+

:1
+

+1
I

21.22

r
DOD.
DODD

+
+

FIRST
HOLE

10.72

BOTTOM
PAN

11 :

.--

---- •

L~ ~

-'---

1~·44

CP-0273

Figure 2-3

Chassis Slide Mounting

Remove the drive top cover and remove the mounting screw and shipping strap from the
linear positioner (Figure 2-1 b). Turn the shipping strap upward and replace it on the linear
positioner. Pull the heads forward as far as possible without going off the ramp (Figure 1-7)
and confirm that the batteries (Figure 1-1) return the heads to the home position.
2-4

6. Inspect P2 (Figure 4-17) and the spindle pulley to ensure that the drive is configured properly for the input power to be used. If P2 contains two jumpers, the supply is configured for
115 Vac operation. IfP2 contains only one jumper, the supply is configured for 230 Vac. The
operating frequency is stamped on the spindle pulley.
7. Check the logic assembly to ensure that no pins are bent or broken; then plug the interface
cable card into card position 7 or 8 of the logic assembly. If there is only one drive in the
system, or if this is the last drive of the daisy-chain, ensure that an M930 terminator card
(Dwg. No. RK05-0-2) is in the unused interface card position.
8. If RK05-type drives are daisy-chained with RK03 drives in a multi drive installation, arrange
the RK05s consecutively at the controller end of the bus to avoid interruption of the AC
LOW and DC LOW interface lines, which are not carried by the RK03s. If this arrangement
is not possible, connect all RK05-type drives separated on the bus by RK03s by means of
separate cables between their J06 connections (Figure 2-2).
9. If the drive is to be connected to other than an RKII-C or RKII-D controller, install the
interface cables as follows:
a.

Remove the prefilter and frame.

Route the interface cables through the prefilter opening and reinstall the filter and
frame so that the cables fit into the slot on the side of the frame (Figure 2-4).

Route the cables over the prefilter and fold them as indicated in Figure 2-4.

Place the cable retaining bracket over the fold in the cables and fasten the bracket to
the chassis.

10. If the drive is to be connected to an RKII-C or RKII-D controller, install the interface
cables either as described in Step 9, above, (which is preferable) or as follows:
a.

F old the interface cables and route them through the slot just below the prefilter at the
rear of the drive cabinet (Figure 2-4).

Hold the cables in position and replace the bottom cover.

11. To avoid random errors, confirm that the grounding strap is firmly in place between the
base plate and the chassis, and that brushes are mounted securely and in the proper plane.
Confirm that all connectors are securely in place.
12. Configure the M7700 or M7680 select switch to address a valid drive (Paragraph 3.2.2).
i 3.

Piug the power cord into the switched ac Hne receptacle.

14. Turn the processor keyswitch ON to apply power to the drive.
15. Check that the spindle is clean~ and that the heads are not bent or dirty.
16. Install a test cartridge on the spindle (Paragraph 5.4.1) and check the head alignment with a
checking scope. Then run the appropriate diagnostic tests to ensure proper electrical and
mechanical drive operation.

2-5

A = SINGLE FOLD
B =DOUBLE FOLD

B
B

PREFILTER FRAME

INTERFACE CABLES

RETAINING BRACKET

•

IF CABLE STICKS OUT TOO FAR
ON LEFT IT WI LL BE DAMAGED
WHEN DRIVE IS PULLED OUT OR
PUSHED INTO CABINET

Figure 2-4

RK8/E Interface Cable Installation
2-6

2.3 CARTRIDGE-HANDLING PRACTICES AND PRECAUTIONS
The following precautions and cartridge-handling practices must be observed with all RK05 and
RK05-J cartridges, and with all RKOS-F cartridges prior to their permanent installation into their
RKOS-F drives.
1. Store cartridges in a clean, dry area away from direct sunlight. Do not expose cartridges to
heat. They may be stored on edge or stacked; however, stacks of more than 3 or 4 cartridges
should be avoided. Do not place heavy items on the plastic cartridge cases. Do not store
cartridges on top of computer cabinets or in places where dirt can be blown by fans into
cartridge interiors.
2. Whenever a cartridge is not in a drive, enclose it in a plastic bag to exclude dust or dirt.
3.

Professional cartridge cleaning is required every six months; however, disks should be cleaned whenever they are excessively dirty, or when a high transient error rate is encountered.

Place stiff cardboard or plastic labels only in the molded frame at the front edge of the disk
cartridge without using any adhesives. Labels placed on any other part of the cartridge may
interfere with the drive operation or introduce contamination into the drive or the interior of
the cartridge.

Allow the temperature of the cartridge to become stabilized with the room temperature
before using the cartridge. If cartridges are exposed to outside temperature extremes, or if
the temperature differential between drive and cartridge exceeds 20° F, a two-hour stabilization period is necessary.

6. Although cartridges recorded on RK03s, RK05s, and RKOS-Js are fully interchangeable,
allow them to stabilize before new data is recorded on them. Data interchangeability
between drives is only guaranteed if the temperature difference does not exceed 30° F (17°
C), even though a specific drive/cartridge combination may operate over a temperature
range of SO° to 11 0° F (l0° to 43 ° C).
7.

Keep the spindle hub clean and free from nicks and burrs to ensure reliable cartridge operation. Because the hub is slightly magnetic, do not expose it to metal chips that could adhere
to the mounting surface. Periodically inspect the coupling hub on the bottom of the disk
cartridge for dirt, metal chips, plastic chips in cone, etc.

8. A sustained tinging, scratching, or rumbling sound (not to be confused with spindle ground
brushes) that is the result of head-to-disk contact may occur if the cartridge is not properly
seated on the spindle, if excessive contamination has built up in the interior of the cartridge,
or if the cartridge or the drive is defective. If this sound is heard, shut down the drive
immediately to avoid damage to the read/write heads. Remove the disk cartridge and examine the heads for damage or excessive dirt. If necessary, clean or replace the heads. Do not
reuse the cartridge without first checking it for surface damage.
CAUTION
NEVER CYCLE A BAD CARTRIDGE
THROUGH AN INSTALLATION OF SEVERAL
DRIVES. This practice can ruin all the read/write
heads or contaminate all drives in a multidrive installation, which will in turn damage all other cartridges
run in these drives.
9.

Always keep the front door of the drive closed and keep all covers on to prevent unnecessary
entry of atmospheric dirt or dust.
2-7

2.4 CARTRIDGE PACKING AND SHIPPING
Data recorded on disk cartridges may be degraded by exposure to any sort of small magnet brought
into intimate contact with the disk surface. If cartridges are to be shipped in the cargo hold of an
aircraft, precautions are necessary against possible exposure to magnetic sources. Because physical
separation from the magnetic source is the best protection against accidental erasure of a cartridge,
cartridges should be packed at last three inches within the box. This amount of separation should be
adequate to protect against any magnetic sources likely to be encountered during transportation,
making it generally unnecessary to ship cartridges in specially shielded boxes.
2.S NORMAL OPERATING PROCEDURES
All drives in a multi drive system must have operating power applied even when the drive is not in use.
In addition, unused drives should be left write-enabled, with the RUN/LOAD switch in the LOAD
position.
IMPORTANT
ON EARLIER MODEL RK05 DISK DRIVES
EQUIPPED WITH A POWER ON/OFF
SWITCH, DO NOT USE THE ON/OFF
SWITCH DURING SYSTEM OPERATION TO
REMOVE OPERATING POWER FROM AN
INDIVIDUAL DRIVE.
Because the DC LOW interface signal is common to all drives in a multi drive system, a power loss in
anyone drive disables all the drives in the system. If the drive power is controlled by a processor
keyswitch, all drive ON/OFF switches should be left ON; however, all RUN/LOAD switches should
be set to LOAD before system power is removed.
2.S.1 RKOS and RKOS-J Cartridge Loading
The procedure for cartridge loading is as follows:
1. Set the R UN LOAD switch on all drives to LOAD and observe that the LOAD indicator
lights.
CAUTION
If the LOAD indicator is not lit, the drive front door
is locked. In this case, do not attempt to force the
front door open.
2. Open the front door of the drive and gently insert a clean, operable disk cartridge fully into
the cartridge receiver. DO NOT TWIST OR FORCE THE CARTRIDGE DURING
INSERTION!
3. Close the front door of the drive and set the RUN/LOAD switch to RUN.
4. Wait for the RDY and ON CYL indicators to light; the drive is now ready to perform seek,
read, or write operations.
2.S.2 RKOS and RKOS-J Cartridge Unloading
The procedure for cartridge unloading is as follows:
1. Set the RUN /LOAD switch to LOAD and observe that the RDY indicator goes out. After
approximately 30 seconds, the LOAD indicator will light.
2. Open the drive front door and gently withdraw the disk cartridge.
2-8

3. If another cartridge is not loaded, close the drive front door to prevent unnecessary entry of
atmospheric dirt or dust.
4. Store the cartridge in a clean plastic bag.

2.5.3 RK05-F Cartridge Installation
The procedure for installing cartridges in the RK05-F Disk Drive is as follows:
1. Remove power from the drive.
2.

Remove the top and bottom covers and the front bezel.

3. Attach springs to the cartridge, using screws already in the cartridge (Figure 2-5). Point the
hooks of the springs toward the cartridge access door. Restart screws by rotating them
backward (counterclockwise) until the lead threads pass each other and the screw drops into
the hole in the cartridge body with an audible click; the screws then should drive easily in the
normal (clockwise) direction.

HOLD DOWN
SPRINGS

Figure 2-5

RK05-F Cartridge

4. Install plastic door-opening wedge. The circular slots in the wedge snap around the top of
the
retainerTTbutton,
which is pulled up through the top of the cartridge when the access
door
________ ..1
__ .. 1__ i.'! __ .. _1_ .. !.L' .. L ____ !_1 _ •• _ L ___ .L' .. L ____ .. _!-1 __ 1- __ ! __ .•. ! .. t.. A
D •••
..
~

t..~

1:S Upt::Ilt::U. u:st:: LIlt: llr:SL :slULU LIlt: :st:lHllIlUllIUt:I VI lIlt: ~ClIllIU!5t: Ut:!5IlI., WIlll f"'\. Vi .LJ, u.,~ \.1i~

second slot if the serial number begins with S.
5. Carefully guide the cartridge into position in the duckbill and over the cartridge-support
posts. Hook the springs under the front lip of the base casting (Figure 2-6). Do not overstretch the springs when installing or removing cartridges.
2-9

HOLD DOWN
SPRINGS

Figure 2-6

RK05-F Cartridge Installed

2.5.4 RK05-F Cartridge Removal
The procedure for removing cartridges from the RK05-F Disk Drive is as follows:
I.

Remove power from the drive.

Remove the top and bottom covers and the front bezel.

3. Unhook the springs from the front lip of the base casting. (Do not overstretch the springs.)
U sing the cartridge handle, lift the cartridge straight upward. When the cartridge hub has
separated from the magnetic spindle, remove the cartridge from the drive. Take care that the
springs do not catch on anything during the removal process.
4.

Remove the wedge, permitting the access door to close so that the interior is protected from
dust.

5. Remove the springs from the cartridge before returning it to the box.

2-10

CHAPTER 3
INTERFACE

3.1 GENERAL
The flexibility achieved with the address select logic and the eight-position address select switch permits drives in the RK05 family to be connected to a variety of computer systems. In the RKII-C and
RK8jE systems, up to four logical drives can be serially connected to a single bus; in the RKII-D
system, up to eight logical drives can be serially connected. (Each RK05-F Disk Drive is equivalent to
two logical drives contained in a single unit.)
Interface cable connection of the RK05 Disk Drive is made to card position 7 or 8 of the electronic
module. These card positions are parallel-wired so that several drives may be daisy-chained in a multidrive configuration; that is, card position 7 or 8 of the first drive is connected to card position 7 or 8 of
the succeeding drive, etc. (By convention, card position 7 is used for input signals; card position 8 is
used for output signals.) If there is only one drive in the system, an M930 terminator card must be
installed in the unused interface card position; if there is more than one drive in the system, only the
last drive on the bus must have the M930 terminator card in the unused interface card position. The
interface signal levels are determined by the M930 terminator card. An assertion, or logic 1, is approximately +0.5 Vdc, and a negation, or logic 0, is approximately +3.5 Vdc.
Figure 3-1 illustrates and the following paragraphs describe the function of each interface line. The
signals listed, being bus signals, operate according to negative logic; they are asserted low.
3.2 INPUT INTERFACE LINES
3.2.1 RKII-D
This line (BUS RKII-D L) transmits a signal that configures the address select logic to operate with a
particular controller type. A logical 0 on this line indicates that the controller is not an RKI1-D (thus,
the controller is either an RKI1-C or an RK8jE, both of which control only four drives on a single
bus), while a logical 1 indicates that the controller is an RKII-D.
3.2.2 Select (4 Lines)
BUS SEL DR 01 AlE, IjBjF, 2jCjH, and 3jDjJ L operate in conjunction with the RKII-D interface
line and an eight-oosition address select switch on the M7700/M7680 card to determine the drive
address assigniitent and selection by one of the following two methods:
1.

With a logical 0 on the RKII-D line, the M7700jM7680 selection circuit is configured to
decode the four selection lines as a linear set. In a particular drive, only one of the four lines
is internally connected (via positions 0 through 3 of the address select switch) to the drive
control logic. To select a drive, the controller places a logical 1 on the desired select line.
This line remains at logical 1 during the entire data transfer or control operation. (RK05-F
drives can occupy positions 0 and 1 or 2 and 3, and can be selected by a logical 1 on either of
the two positions.)

3-1

BUS RK11D-L

~ A 07 U1

BUS SEL DR '/J/A/E L

---.

BUS SEL DR lIB/F L

I
I

BUS SEL DR 2/C/H L

A 07 K2
A 07 L2

BUS SEL DR 3/D/J L
BUS CYL ADD 0 L

A 07 K1

BUS CYL ADD 1 L
BUS CYL ADD 2 L

A 07 L1

BUS CYL ADD 3 L

A 07 C1

BUS CYL ADD 4 L

A 07 F1

LL.~

BUS CYL ADD 5 L

A 07 Jl

A 07 E1

Ir
lJJ

..J
..J

0
Ir

I
I

A 07 Dl

BUS CYL ADD 6 L
BUS CYL ADD 7 L

A 07 Hi

BUS STROBE L

B 07 HI

BUS HEAD SELECT L

B 07 M2

BUS WT PROTECT L

B 07 R2

BUS WT DATA a CLK L

A 07 F2

BUS WT GATE L

B 07 L2

BUS RESTORE L

A 07 M1

BUS RD GATE L

B 07 R1

BUS FIL E READY L

B 08 N1

BUS R/W/S RDY L
BUS ADDRESS ACCEPTED L

A 08 H2

BUS ADDRESS INVALID L

A 08 T2

BUS SEEK INCOMPLETE L

A 08 S2

BUS WT PROT STATUS L

B 08 P1

0
Ir

BUS WT CHK L

B 08 K1

BUS RD DATA L
BUS RD CLK L

B 08 SI

BUS SEC CNTR '/J L

B 08 L1

BUS SEC CNTR t L

A 08 P2

BUS SEC CNTR 2 L

B 08 K2

BUS SEC CNTR 3 L

B 08 J1

BUS SEC PLS L

B 08 N2

BUS INDX PLS L

B 08 M1

BUS AC LO L

B 08 F1

BUS DC LO L

B 08 F2

BUS RK05/HIGH DENSITY L

B 08 P2

CONTROLLER

I
I

A 07 M2

a...

A 07 J2

0::
lJJ

..J
..J

tt-

a...
t~

0
10

II
I
I

lJJ

>
Ir
a
~
en
C

II o

A 08 R2

B 08 S2 I

CP- 0841

Figure 3- I Controller /RK05 Disk Drive Interface Lines and Pin Assignments

3-2

With a logical 1 on the RKII-D line, the M7700/M7680 selection circuit is configured to
decode the four selection lines as a binary-encoded set. To select a drive, the controller
places a 3-bit binary code, which corresponds to the drive address, on these select lines. This
binary code is then translated by a three-line-to-eight-line decoder to activate only one of the
eight address select switch positions. (RK05-F drives can occupy positions 0 and 1,2 and 3,
4 and 5, or 6 and 7; selection of either of the positions occupied by a drive selects that drive.)

The M7680, which is completely downward-compatible with the RK05-J, differs from the M7700 only
in that it generates an ODD DRIVE L signal by decoding the input select lines. This signal, which is
completely internal to the drive, determines whether the outer (even) or inner (odd) half of the disk is
used.
The RK05-J /RK05-F select switch, when in the "F ," or closed position, wires drive select positions
together by pairs (0/1,2/3,4/5,6/7). The "J," or open position, maintains downward compatibility.
3.2.3 Cylinder Address (S Lines)
BUS CYL ADD 0 L through BUS CYL ADD 7 L determine the cylinder position of the read/write
heads. In order to move the heads to a desired cylinder, the controller places a corresponding 8-bit
binary code on the lines (valid codes = 0 through 20210). These lines are gated by the Strobe signal to
position the heads at the selected cylinder. The binary code remains on the lines until either the
Address Acknowledged or the Address Invalid signal is returned from the drive (Paragraph 3.3.3).
3.2.4 Strobe
BUS STROBE L transmits a signal that gates the Cylinder Address or Restore line. The controller
places a logical 1 on the Strobe line only after the Cylinder Address or the Restore signals are fully
settled on their respective lines. The Strobe line remains at logical 1 until either the Address Acknowledged or the Address Invalid signal is returned from the drive.
3.2.5 Head Select
BUS SEL UPPER HD L transmits a signal that determines which of the two read/write heads is to be
selected. The controller places a logical 1 on this line to select the upper head, and a logical 0 to select
the lower head. Either signal remains on the line throughout the entire read or write operation.
3.2.6 Write Protect Set
BUS WT PROTECT L transmits a signal that disables the drive write amplifiers to prevent a write
operation. The controller places a logical 1 on this line to set the Write Protect flip-flop and inhibit the
write capability of the drive. The Write Protect flip-flop is also set if the WR PROT indicator is off and
the operator presses the WT PROT switch.
3.2.7 Write Data and Clock
BUS WT DATA & CLK L transmits multiplexed data and clock pulses to the disk drive.
3.2.S Write Gate
BUS WT GATE L transmits a signal to simultaneously turn on both the write and erase current in the
selected write head. The controller places a logical 1 on this line 1 J.LS prior to transmitting the write
data. This line remains at logical 1 throughout the data transmission time.
3.2.9

Restore (RTZ)

"Ill T~ 1}
P~T()1} P T t .. <)..,~t"t"I;t~ <) ~; ..... ..,<)1 t" n"~;t;".., tha ..a<:lrt In,.,.;ta ha<:lrt~ <:It ""l;nrta.,. 7 a.,. "
Tha ""nt.,."l1~.,.
.&.'-..L..fU.I..",.A.,.L..I..L..I .... J.U..lJ.r.3.l11.l1L..:J U. t.JI.l6J..I.U.J. I.V pVt.JI.l ... .I.V.l.l \,..1.1" J..""'UUI T'fJ...I.L,."", .I..I.""UO ""'" ""].1..1.1..1.""''-'''' "'-".I.U' ...... .1..1."-" ""''-'.1..1. ...... ''' ...... '-'..1.

...,'-"....,

places a logical 1 on this line prior to issuing the Strobe (BUS STROBE L) signal. About 2 J.LS after this
signal is issued, the drive returns an Address Acknowledged signal, clears the address register, and
moves the heads to cylinder zero. The Restore line remains at logical 1 until the Address Acknowledged signal is received by the controller.

3-3

3.2.10

Read Gate

BUS RD GATE L transmits a signal that allows data to be read from the drive. The controller places a
logical 1 on this line to enable the Read Clock and Read Data output lines. This line remains at logical
I throughout the entire read operation.

3.3

OUTPUT INTERFACE LINES

3.3.1

File Ready (Drive Ready)

BUS FILE RDY L transmits a logical 1 to indicate the following conditions:

1.
2.
3.
4.
5.
6.
7.
3.3.2

Drive operating power is correct.
A disk cartridge is properly loaded.
The drive front door is closed.
RUN /LOAD switch is in the RUN position.
Spindle is rotating at the correct speed.
Read/write heads are loaded.
W rite Check is false.

Read, Write, or Seek Ready/On Cylinder

BUS R/W /S RDY L transmits a logical 1 to indicate that the drive is in the File Ready condition and
is not performing a seek operation.

3.3.3

Address Accepted

BUS ADDRESS ACCEPTED L transmits a 5-J.ls negative pulse to indicate that the drive has accepted
a Seek command with a valid address and the command execution has begun. The negative pulse is
generated about 2 J.l,S after receipt of the Strobe signal, even if there is no change from the present
address.

3.3.4 Address Invalid (Logic Address Interlock)
BUS LOG ADD INT L transmits a S-J.lS negative pulse to indicate that the drive has received a
nonexecutable Seek command with a cylinder address greater than 202. For this case, the Seek command is suppressed in the drive and the heads are not moved. The pulse generation time is the same as
for the Address Acknowledged signal.

3.3.5 Seek Incomplete
B US SIN L transmits a logical 1 to indicate that some malfunction in the drive did not allow the seek
operation to be completed. This line remains low until a Restore command is received or the operator
sets the RUN/LOAD switch to LOAD and then back to RUN.

3.3.6 Write Protect Status
BUS WT PROT STATUS L transmits a logical 1 to indicate that the write capability of the drive is
inhibited (write-protected). When this line is at logical 1, the WT PROT indicator on the drive control
panel lights.

3.3.7 Write Check
BUS WT CHK L transmits a logical 1 to indicate the following conditions:

1.
2.

Erase or write current without a WRITE GATE.
Inoperative linear positioner transducer lamp.

When the Write Check signal is at a logical 1, all external commands to the drive are suppressed and
the FA UL T indicator on the drive control panel lights. If the fault condition is temporary, the operator may turn off the FAULT indicator by pressing the WT PROT switch. This action, however,
causes the V,lT PROT indicator to light; the WT PROT switch must be pressed a second time to turn
off the WT PROT indicator.

3-4

3.3.8 Read Data
BUS RD DATA transmits read data only (l60-ns pulses).
3.3.9 Read Clock
BUS RD CLK L transmits read clock pulses only (l60-ns pulses).
3.3.10 Sector Address (4 Lines)
BUS SEC CNTR 0 through 3 L indicate which sector is passing under the read/write heads. The sector
address is a 4-bit binary code derived from the Sector Address counter.
3.3.11 Sector Pulse
BUS SEC PLS L transmits a 2-fJ,s negative pulse each time a sector slot passes the sector transducer.
The index slot (unique slot) is suppressed in this line and is transmitted on a separate Index Pulse line.
3.3.12 Index Pulse
BUS INDX PLS L transmits a single 2-fJ,s negative pulse for each revolution of the disk. The Index
Pulse occurs 600 fJ,S after the last sector pulse and is generated each time the index slot (unique slot) is
detected by the sector transducer.
3.3.13 AC LOW
BUS AC La L transmits a logical 1 when there is a loss (for more than 45 ms) of the 30 Vac within the
drive. When AC LOW occurs, the drive finishes reading/writing the current sector, then initiates a
normal head-retract and unload cycle. If a total power loss occurs before the heads are completely
retracted, the safety relay is de-energized to retract the heads under battery power (emergency retract).
3.3.14 DC LOW
BUS DC La L transmits a logical 1 when the ± 15 Vdc within the drive drops to 12 Vdc or below.
When DC LOW is generated, the safety relay is de-energized to retract the heads under battery power
(emergency retract). Since the RUN gate of each drive is connected to the DC LOW bus, a DC LOW
signal from anyone drive in a multi drive system disables all the drives in the system.
3.3.15 High Density /RK05 L
BUS RK05 L transmits a logical 1 (indicating high density only) whenever the drive is selected. (All
RK05s are high density.)

3-5

CHAPTER 4
THEORY OF OPERATION

4.1 FUNCTIONAL DESCRIPTION
Figure 4-1 illustrates the major areas and associated signals of the RK05 Disk Drive. Together they
rotate the recording disk, align the heads at a specified cylinder, and perform the read and write
functions.
Paragraphs 4.1.1 through 4.1.5 describe the major operations of the disk drive; Paragraphs 4.2.1
through 4.5 describe the detailed logical sequence of each major operation.

4.1.1 Start
During the start cycle, the control and interlock logic controls the spindle motor operation. To energize the spindle motor, the RUN/LOAD switch must be in the RUN position and operating power
must be applied. In the case of the RK05 and RK05-J, the drive front door must be closed and the disk
cartridge must be properly installed.
If these interlock conditions are fulfilled, the spindle motor is energized. After an 8-second delay, to
allow the spindle to accelerate to operating speed, the control and interlock logic generates an internal
LOAD HEADS signal, which loads the read/write heads and positions them at cylinder zero (Paragraph 4.2.5.1). When the heads are loaded and positioned at cylinder zero, the RDY and ON CYL
indicators light, and the BUS FILE RDY and R/W /S RDY ION CYL interface lines go low.

Figure 4-2 illustrates the logical sequence during the start cycle. Paragraph 4.2.2 contains a detailed
description of the preceding sequence.

4.1.2 Stop
The disk drive can enter a stop cycle in three ways:
1.
2.
3.

Placing the RUN/LOAD switch to LOAD
Losing spindle speed
Losing operating power in any drive on the bus.

If any of the preceding conditions occur, the control and interlock logic removes the internal LOAD
HEADS signal and brings the BUS FILE RDY interface line high. When LOAD HEADS is removed,
the positioner control logic retracts the read/write heads. After the heads are fully retracted, the
spindle motor is de-energized and the spindle coasts to a stop (about 30 seconds). When the spindle has
stopped rotating, the LOAD indicator lights and, in the RK05 or RK05-J, the drive front door
uniocks.

Figure 4-3 illustrates the logical sequence during the stop cycle. Paragraph 4.2.3 contains a detailed
logic description of this sequence.

4-1

RK- 110

•

HEAD SELECT 1

·1 WRITE

~,---~----

WRiTE GATE 1

1 WRITE

WRITE DATA 1
S CLOCK
WT PROT SW 1

READI
WRITE
LOG IC

READ GATE 1I

I
I
CYLINDER
ADDRESS(S)

I
I
STROBE
I
RESTORE
I

~ROTE:;

STAT _'S

CHECK

READ DATA
RE AD CLOCK

I
1
1
1

SELECT (4)

- - J ADDRESS ACCEPTED

-...J ADDRESS INVALID
--JR/W/S READY

COUNT PULSE FWD

CONTROL S
I SECTOR
SEQUENCING - - : ADDRESS(4)
DIFF(5)
~SECTOR PULSE
r---F-W-D------------------------+-+---------------------~
---lINDEX PULSE
COUNT PULSE REV

0::

....J
....J

o0::

'SEEK
----+I INCOMPLETE

REV

....J
....J

0::

RTZ

0::

o
U

o
u
SECTORI
INDEX

LINEAR
POSITIONER
CONTROL

o::.:::

::.:::
0::

0::

t t
I

LOAD
HEADS,

SPINDLE MOTOR RELAY

INTERLOCK
INDEX
RUNI
SPINDLE
LOAD SW ~ CONTROL

_I
I

I
I

AC LOW

-' DC LOW

::
I

FILE READY

:15Vdc

30Voc

NOTE
INSERT A ' RK05,RK05J
Ir..JSERT B ' R!o(05F

CP-0271

Figure 4-1

Functional Block Diagram

M7701
GENERATE AC
OR DC LOW

DISABLE
RUN GATE

M7701
RESET FAULT
LATCH
RESET WT PROT
ENABLE START
DELAY COUNTER

ENABLE
LOAD HEADS
GATES

GENERATE
R/W/S READY
II

a L1GHT ON
CYL"
M7701
SET READY

FLIP-FLOP
LIGHT RDY INDIC
GENERATE
READY L
CP-0241

Figure 4-2

Start Flowchart
4-3

RUN/LOAD
TO LOAD

* DC LOW

SPINDLE
SPEED LOW

*AC LOW

M7701
ENABLE DISK
STOPPED
COUNTER

M7701
DISABLE
RUN GATE

M7701
SPINDLE SPEED
TEST TIMED
OUT

M7701

M7701
CLEAR START
DELAY COUNTER
I F NOT ALREADY
CLEARED

I-----I~ SECTOR

INTERVAL
INCREASES

YES

_._----------,
M7701
* TRANSIENT POWER LOSS ONLY.
TOTAL POWER LOSS CAUSES
EMERGENCY SHUT DOWN.

UNLOCK DRIVE
FRONT DOOR
(RK05 OR RK05J)

CP-0240

Figure 4-3

Stop Flowchart

4-4

4.1.3 Track Addressing and Head Positioning
To move the read/write heads from a current location to a new location above the disk (a seek operation), a selected drive must first receive an 8-bit binary cylinder address from the controller. If the new
address exceeds cylinder 202, the BUS ADDRESS INVALID L (Logic Address Interlock) interface
signal is generated and head motion is suppressed. If the new address does not exceed cylinder 202, the
BUS ADDRESS ACCEPTED L interface signal is generated and the new address is compared to the
current address. The comparison result (difference) is fed to a positioner servo system to move the
heads.
As the heads pass each cylinder, output pulses from the linear positioner transducer trigger a Difference register to control the velocity of head motion (Paragraph 4.3). As the heads approach the destination cylinder, the head positioner decelerates, eventually stopping the heads at the designated
cylinder. After a small delay, to allow the heads to settle at the new location, the ON CYL indicator on
the control panel lights and the R/W /S READY interface line goes low.
If at any time during the seek operation a return-to-zero (Restore) command is received, or the heads
reach the inner limit of the disk, the seek operation is immediately terminated and the heads are
retracted to cylinder zero of the logical drive currently selected.

Figures 4-4 and 4-5 illustrate the logical sequence during a seek or return-to-zero operation. Paragraph
4.2.5 contains a detailed logic description of this sequence.
4.1.4 Recording Technique
Each head is a four-terminal, magnetic device containing two coils. A center-tapped coil performs the
read or write function, while the other series-connected coil performs the erase function. The head
(Figure 4-6) is designed so that the erase coil is electrically connected to the center tap of the read/write
coil and is energized (Figure 4-7) whenever a write operation occurs. This head configuration, called
"straddle erase," erases most of the residue from previous recording between the tracks and thus
eliminates track "crosstalk" or interference from such recording. The RK05 and RK05-J data tracks
are O.OO7-inch wide with 0.OO3-inch erased separation bands. RK05-F data tracks are 0.OO4-inch wide
with O.OOI-inch erased separation bands. True center-to-center spacings are O.OlOOOO-inch in the RK05
and RK05-J and 0.005053-inch in the RK05-F. During a write operation, current through the write
coil automatically overwrites old data.
The RK05-type drives use a double-frequency, non-return-to-zero (NRZ) method of magnetic recording. In this method, flux reversals (clock pulses) are recorded on the magnetic disk at regUlarly-spaced
intervals (Figure 4-8). The time period between these clock pulses is a bit cell, and data storage occurs
within these cells. A flux reversal during a bit cell represents a logical I ; the absence of a flux reversal
during a bit cell is a logical O.
4.2

LOGICAL DESCRIPTION

4.2.1 Power ON/OFF Sequ.ence
Application of ac power lights the PWR indicator, turns on the blower, and energizes the various
voltage regulators. If ac power is removed when the read/write heads are not in the "home" position,
the home microswitch applies battery power to the linear motor, retracting the heads to "home."
4.2.2 Start
Figure 4-9 is a block diagram illustrating the control and interlock aspects of the start/stop cycle.
Although some logic elements are indicated, this figure is principally intended to simplify the actual
gating and signal flow. If any gate-chasing or logic analysis is anticipated, refer to the M7701 circuit
~chematic.

4-5

M7680/~M~7~7~0~0~~~__,

M7701
DO NOT
GENERATE
SELECT/READY

M7680/
M7700
GENERATE SEEK
INCOMPLETE

ENABLE SEEK
INCOMPLETE
COUNTER
r - - - - - - 1 REMOVE R/W/S
READY
TURN OFF
"ON CYL"

M7681/
M7702
SEND ADDRESS
INVALID

M7681/
M7702
CONFIGURE DIFF
REG FOR HI VEL

G938/
G938 YA
YES

RETAIN SERVO
,POS:T:CN t.~ODE

SET FOWARD
FL I P - FLOP

TR IGGER SETTLE
DELAY
ENABLE SERVO
POSITION MODE

GENERATE R/W/S
READY
DISABLE SEEK
INCOMPLETE
COUNTER
LIGHT "ON CYL "
CP -0276

Figure 4-4

Seek Flowchart

4-6

OUTER LIMIT

INNER LIMIT

DO NOT
GENERATE
SELECT/READY

M7681/M7702

....--_"&""_-"""

SET OUTER
LI M IT EXT.
LATCH
'RESET REVERSE
1\.
FLIP-FLOP
,
SET FORWARD
FLIP-FLOP

. M7681 / M7702

--_...&-_-.....,
CLEAR NEW
ADDRESS REG
CLEAR
CURRENT
ADDRESS REG
SET REVERSE
FLIP-FLOP

M7681/
M7702
HOLD CURRENT
a NEW ADD RES S 1 4 - - - - - + 1 1 1 - - - - - - - ,
REGS CLEAR

M7681/M7702
M7680/M7700
G938/G938YA

RESET
FORWARD
FLIP-FLOP
TRIGGER
SETTLE DE LAY
ENA8LE SERVO
POSITION MODE

M7680/ M7700

--_...&-_--

M7681 / M7702
RESET OUTER
LI MIT EXT.
LATCH

GENERATE
R/W/S READY
DISABLE SEEK
INCOMPLETE
COUNTER
LIGHT "ON CYL"
CP-0275

Figure 4-5

Return-to-Zero (Restore) Flowchart

4-7

.:.. : ::.......:
.:":::.::::-.

:;:

__Ifo~:' "'"'
....
. .,::
'

ERASE POLE

HEAD
SLIDER
PAD
CP-02S7

Figure 4-6

INPUT FROM
WRITE DRIVER
OR
OUTPUT TO
READ AMPLIFIER

Read/Write Head

READ/WRITE
COIL

HEAD SELECT

CP-0258

Figure 4-7

Simplified Read/Write Head Circuit

4-8

I.....- - - - - - - - 3 BIT CELL TIM E S ------------.1-1
I

j.--BIT CELL TI ME

----l

I
CLOCK
MULTI PLEXED
DATA

{
WRITE DATA

I
I

0 ~~~-:)\ I ((~~ r,=)'t
.JJ \2- ______ ...,
1 \ \......, J
I

SIGNAL AT READ HEAD

----.-'

\. _ _ ) )

I ...... -

I\r-

(;=-~~~~ It::

\. _ _ _ _ _ ) }

-.-' I ...... - - - -

14 ~

1 '-..:

/:J

:Ai

-~I---~~---~I-~~~I-~~-~I---~~--~I~
I

~I~

LJJ

IIr

AMP~F~~~ llJ
OUTPUT

II..--__..J:

I :L

I
FLUX
REVERSALS

I
I
~~I-------O------~I-I
I
I
I

L-J:

I
I

I
WRITE F-F

L!J
I

III
~

CP-0259

Figure 4-8

Double Frequency Pulse Relationship

4-9

- _... _ - - . _.....-._... _--........-.--..... -...........- _. . . -. _ - _ . _ - . ····-·--··----·-··-----·----1 DC
LOW

-------01

+5V

1
1

+15V
-15V

SAFETY
RELAY

RUN L

DC OK
INTERLOCK.__________G_A_T_E__________~

RUN/LOAD
LATCH

RUN
GATE

40jl5

R STROBE

1-----0
SPINDLE
MOTOR
LATCH

SPINDLE
MOTOR
RELAY

R
HOME~+-----------------------

R/S/W READY~+------------------------------------

LOW SPEED
TIME OUT
SECTOR

+:>I

DIS>(
STOPPED
COLNTER
SECTOR/INDEX~--------~------------------+_~

\ - - - - - - 1 LOW

RUN
STROBE

RUNILOAD LOAD
SW ITCH C>-__+--C]

I
I
I
I
I
I
I
I
I
I
I

r----------------------------------i~~~gs

I
1---------------IS

30 VAC
45ms

START
DELAY
COUNTER

AC LOW
DETECT

READY

R
LOAD HEADS
GATE

HOMEr---NO POSITION I
LAMP----

READY
FLIP-FLOP

___-II

WRITE
CHECK

I
1
WT PROT
LATCH

C
SET WT

L--------------------------------------;s
Ru/V STROBE

Figure 4-9

_________________________________-11 WRITE
WRITE
PROTECT
FLIP-FLOP

Control and Interlock Block Diagram

PROTECT

Placing the RUN/LOAD switch on the front control panel in the RUN position enables the Run gate,
provided that the +15 and -15 Vdc are above 12 Vdc and the +5 Vdc is above 4.6 Vdc (Paragraph
4.2.3.4), and in the case of the RK05 and RK05-J, that a disk cartridge has been properly installed and
the drive front door is closed and locked.
With the Run gate enabled, the spindle motor latch is set to energize the spindle motor relay and
initiate disk rotation. At the same time, the Start Delay counter begins to count pulses (at a rate of one
pulse per second) from the Slow Clock. When a count of eight (8 seconds) is reached, a feedback
output from the counter prevents it from incrementing further. By this time, if the spindle has accelerated to the correct operational speed (Paragraph 4.2.3.2), the set output from the On Speed flip-flop is
ANDed with the Start Delay counter output to enable the Load Heads gate and produce the LOAD
HEADS signal. This signal enables the D input of the Ready flip-flop, and also allows the positioner to
move the read/write heads to cylinder zero (Paragraph 4.2.5.1). Once the heads are positioned and
settled at cylinder zero, the signal R/W /S READY is produced, lighting the ON CYL indicator
(M7680/M7700) and clocking the Ready flip-flop set. When the Ready flip-flop sets, the BUS FILE
RDY interface signal is produced and the RDY indicator on the control panel lights. The drive is then
ready to perform a seek, read, or write operation.
4.2.3 Stop
The following paragraphs describe the ways that the disk drive can enter a stop cycle. Figure 4-9
illustrates some of the logic elements used in a start/stop cycle. These logic elements are located on the
M7701 card.
4.2.3.1 Normal Stop - Placing the RUN/LOAD switch in the LOAD position enables the Disk
Stopped counter and disables the Run gate, causing RUN L to come high. Once enabled, the Disk
Stopped counter begins to increment; however, it is reset repetitively by every SECTOR/INDEX pulse
before it reaches a count of two. This counter reset technique keeps the door unlocking solenoid deenergized in the case of the RK05 or RK05-J to prevent the operator from opening the drive front door
before the disk has come to a complete halt.
RUN L high clears the Start Delay counter, disabling the Load Heads gate, thus removing the LOAD
HEADS signal. Once cleared, the Start Delay counter must again increment to eight before the LOAD
HEADS signal can be regenerated. This practice allows the heads to fully retract or unload before they
can be loaded again. Removal of the LOAD HEADS signal resets the Ready flip-flop and also allows
the positioner to retract the read/write heads (Paragraph 4.2.5.3). When the heads have fully retracted,
the home microswitch closes to generate the HOME L signal. HOME L resets the Spindle Motor
latch, de-energizing the spindle motor and allowing the spindle to coast to a stop.
As the spindle decelerates, SECTOR/INDEX pulses occur at a slower rate. Approximately 30 seconds
after the Disk Stopped counter is enabled, the disk stops rotating, SECTOR/INDEX pulses cease, and
the Disk Stopped counter is incremented by two pulses from the Slow Clock. When the counter
reaches two (2 seconds from receipt of the last SECTOR/INDEX pulse), a feedback output from the
counter prevents it from incrementing further, while the counter set output energizes the RK05 and
RK05-J door-unlocking solenoid and lights the LOAD indicator on the control panel. The drive front
door can now be opened and the cartridge removed.

4-11

4.2.3.2 Low Speed Stop - When the disk is rotating at normal speed (1500 rpm), INDEX pulses are
generated every 40 ms to trigger the 41 - 49 ms Low Speed Time Out one-shot. The one-shot output is
applied to an associated On Speed flip-flop. As long as the spindle rotation remains above an unsafe
speed, successive INDEX pulses keep the On Speed flip-flop set, thus maintaining the LOAD HEADS
signal. If the spindle speed drops below approximately 1200 rpm, the INDEX pulse interval increases
beyond 50 ms. If this occurs, the Low Speed Time Out one-shot expires and resets the On Speed flipflop. With the flip-flop reset, the LOAD HEADS signal is removed, causing the positioner to retract
the read/write heads (Paragraph 4.2.5.3). When LOAD HEADS is removed, the 40 JlS Stop Strobe
one-shot triggers, clearing the Start Delay counter. Once cleared, the Start Delay counter must again
increment to eight before the LOAD HEADS signal can be regenerated. This practice allows the heads
to fully retract (unload) before they can be loaded again.
The remainder of the low speed stop cycle is the same as a normal stop (Paragraph 4.2.3.1).
4.2.3.3 AC Low Stop - During normal operation, the 45-ms AC Low Detect one-shot is repeatedly
triggered set by the presence of 30 Vac. If this voltage is removed for more than 45 ms, the AC Low
Detect one-shot times out. With the one-shot reset, the AC LOW interface signal is generated. Following the AC LOW signal, the drive continues to operate until the next SECTOR pulse to reset the Low
Speed Time Out one-shot. Thus, a data transfer in progress continues until the end of the sector before
the interface signals are removed.
The remainder of the ac low stop cycle is the same as a low speed stop (Paragraph 4.2.3.2). However, if
a total power loss occurs before the heads are completely retracted, the safety relay closes to retract the
heads under battery power (emergency retract) and to maintain the AC LOW interface signal.
4.2.3.4 DC Low Stop - If the + 15 or -15 Vdc drops below 12 Vdc, or if the +5 Vdc drops below +4.6
Vdc, the DC OK gate is disabled. The output from this gate immediately disables the Run gate, deenergizes the safety relay to retract the heads under battery power, and generates the BUS DC LOW
interface signal.
4.2.4 Disk Drive Addressing
For greater flexibility in a multidrive system, a drive address assignment can be changed by changing
the position of the Address Select Switch (SI) on the M7680/M7700 card. This switch operates in
conjunction with the RKII-D interface line plus the address select decoding logic (M7680/M77oo), as
described in the following paragraphs.
4.2.4.1 RKII-D Address Selection - If the operating controller is an RKII-D, the interface signal
BUS RKII-D L is present. This signal, applied through an inverter, enables a three-line-to-eight-line
binary decoder and disables the linear input gates. Thus, when the binary-encoded (BUS SEL DR
0/ A/E L through BUS SEL DR 2/C/H L) drive address is applied through the input gates to the
binary decoder, the decoder translates the 3-bit binary code and activates one of the eight Address
Select switch positions, or in the case of the RK05-F, one pair of positions. (The RK05-F side of the
RK05-F /RK05-J select switch wires four pairs together; thus, selecting either position 0 or 1 selects
both positions.) If the Address Select switch on the M7680/M7700 card has been set to this activated
position, the signal SELECT H is produced. SELECT H, ANDed with the set output from the Ready
flip-flop (M7701) and the reset output from the Fault latch, produces the signal SELECT/READY L.
This signal allows the drive to perform the various control and read/write operations.
4.2.4.2 RKII-C or RK8/E Address Selection - If the operating controller is an RKII-C or RK8/E,
the interface signal BUS RKII-D L is not present. Hence, the three-line-to-eight-line binary decoder is
disabled and the linear input gates are enabled. This circuit configuration connects the BUS SEL DR
lines, as a linear set, directly to positions 0 through 3 of the Address Select switch on the
M7680jM7700 card. If that switch is set to one of the first four positions and the corresponding BUS
SEL DR line is at a logical 1, the signal SELECT/READY L is produced, as described previously in
4-12

Paragraph 4.2.4.1, to select the drive associated with that line. In the case of the RK05-F, the drive
may occupy positions 0 and 1 or 2 and 3; selection of either position occupied by a drive selects the
drive.
4.2.5

Seek

4.2.5.1 Load Heads Seek - Placing the RUN /LOAD switch in the RUN position generates the signal
LOAD HEADS L (Paragraph 4.2.2). Because the read/write heads are in the "home" position at this
time, the signal OUTER LIMIT H (M7681/M7702) is present. This signal is ANDed with the inverted
LOAD HEADS L signal to set the Forward and reset the Reverse flip-flops. In addition, OUTER
LIMIT H sets the Outer Limit Extender latch to hold the New and Current Address registers at O.
In the RK05 and RK05-J Disk Drives, the Q outputs from the New Address register and the Q outputs
from the Current Address register are applied to the subtractor. Use of the Q outputs from the New
Address register effectively complements the new address, allowing ai's complement addition to take
place in the subtractor. During this addition, the second stage of the subtractor performs an endaround carry operation. Because the Current Address register and the New Address register are both
cleared, the remainder from the 1's complement addition is zero; thus, a no-carry condition is produced. The binary 0 from the subtractor is then applied, through exclusive OR circuits and the "> 3"
decoding gate, to set the Difference register to a low-velocity binary output.

NOTE
Low velocity is when all stages of the Difference register are set. High velocity is when all stages are
cleared.
When the Forward flip-flop sets, FWD H and MOVE L are generated. FWD H is applied to the servo
logic to place it in the velocity mode (Paragraph 4.3.1.1) and initiate forward head motion.
As the heads begin to" move at low velocity toward cylinder zero, count pulses are generated by the
positioner transducer (Paragraph 4.3.1). When the heads pass the outer limit of the recording disk,
OUTER LIMIT H goes low, applying a low to the D input of the Forward flip-flop. As the heads
approach cylinder zero, COUNT PULSE REV H (first count pulse after OUTER LIMIT H goes low)
resets the Forward flip-flop. This action removes FWD H and MOVE L, and places the servo logic in
the detent mode (Paragraph 4.3.1.2).
MOVE L high triggers the 6-ms Positioner Settle Delay one-shot (M7680/M7700). When this one-shot
times out, the R/W /S Ready flip-flop sets to disable the Seek Incomplete counter, light the ON CYL
indicator, and generate the BUS R/W /S RDY L signal. BUS R/W /S RDY H resets the Outer Limit
Extender latch.
4.2.5.2 Forward Seek - To move the read/write heads closer to the disk spindle (forward seek), the
controller places an 8-bit binary address on the Cylinder Address interface lines (BUS CYL ADD 0
through 7), transmits a STROBE pulse, and simultaneously addresses the disk drive (Paragraph 4.2.4).
Reception of the STROBE pulse (M7680/M7700) generates the GOOD STROBE L pulse to clock the
cylinder address from the interface lines (M7681/M7702) into the New Address register.
The Q outputs from the New Address register are applied to both the subtractor and the Invalid
A ..J .-J_~~~ T"'\~+~~+~_ , T.... '" ,...l" ... 1-."", r\
1"\.UUI ~~~ .LJ~L~\'-LVI. V ~\;I VI Lll'-' '-l.

,...,.+ .... ,.+ ... " f tho
1\.T onT A rlrl1"&>c;,c;, 1"&>n1c;,t&>1" &>ff&>t't.j"ph, t'nrnnlprnpnt(l thp npw
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n

V,""I.P,""I.L) V.l

& ......

address and thus allows ai's complement addition to take place in the subtractor. During this addition, the second stage of the subtractor performs an end-around carry operation.

4-13

If the New Address register output is greater than 202, the BUS ADDRESS INVALID signal is
generated. If this is the case, the BUS ADDRESS ACCEPTED L signal remains high, keeping the
Forward or Reverse flip-flops reset and preventing the Difference register from changing states.
If the New Address register output is equal to or less than 202, BUS ADDRESS INVALID L remains
high. This signal is ANDed with the output of the Strobe Generator one-shot (M7680/M7700) to
produce the BUS ADDRESS ACCEPTED L signal.
Simultaneously, the complemented New Address register output is added in the subtractor to the
output of the Current Address register. If after this addition process a carry condition has not
occurred, the positioner must either move the heads forward (toward the disk spindle) or retain the
heads at their current location. To determine this fact, the subtractor carry output is inverted by the
exclusive-OR circuits for only a no-carry condition. If the heads are to move forward, the high output
from the "not zero" decoding gate is ANDed with the inverted carry output and applied to the D input
of the Forward flip-flop.
When BUS ADDRESS ACCEPTED L goes low, the Forward flip-flop clocks, generating MOVE L
and FWD H. FWD H is applied to the servo logic to place it in the velocity mode (Paragraph 4.3.1.1)
and initiate forward head motion. MOVE L resets the R/W /S Ready flip-flop (M7680/M7700) to
accomplish the following:
1.
2.
3.

Enable the Seek Incomplete counter.
Remove the BUS R/W /S READY/ON CYL L interface signal.
Turn off the SEEK DONE/ON CYL indicator.

Once enabled, the Seek Incomplete counter begins to count INDEX pulses (40 ms repetition rate). If
the counter reaches a count of seven (seek incomplete condition), the Seek Incomplete latch is set to
generate the BUS SEEK INCOMPLETE L interface signal. If this occurs, the controller must issue a
return-to-zero (Restore) command, or the operator must set the RUN/LOAD switch to LOAD and
then back to R UN to continue normal operation.
I f a seek incomplete has not occurred, and the distance from the present to the destination cylinder is
greater than 31 for the RK05 or RK05-J, or 63 for the RK05-F, an output from the;;?; 32 (or ;;?;64, if an
RK05-F) decoding gate clears the Difference register (M7681/M7702) to a high-velocity binary output. This binary output is applied to the servo logic to move the heads forward at high velocity.
NOTE
High velocity is when all stages of the Difference
register are cleared. Low velocity is when all stages
are set.
As the read/write heads move across each track, output pulses (COUNT PULSE FWD H) derived
from the positioner transducer are generated. As long as the Reverse flip-flop remains reset, each
COUNT PULSE FWD H clocks the Forward flip-flop set and increments the Current Address register. Each time this register increments, the previously described addition process is repeated in the
subtractor.
When the heads are 31 (RK05/RK05-J) or 63 (RK05-F) cylinders from the destination cylinder, the
;;?;32 or ;;?;64 decoding gate is disabled, permitting the Difference register to be decremented directly by
the decoded output of the subtractor. When the heads are 3 (RK05/RK05-J) or 7 (RK05-F) cylinders
from the destination cylinder, the ~3 or ~7 decoding gate is enabled to set the Difference register to a
low-velocity binary output. The Current Address register continues to increment until the heads are
within one-half cylinder of the destination cylinder. At this ooint. the "not zero" decodinsz g:ates is
disabied and the Forward flip-flop is reset, thus removing FWD H and MOVE L.
-U

4-14

FWD H low places the servo logic in the detent mode (Paragraph 4.3.1.2), while MOVE L high
triggers the 6-ms Positioner Settle Delay one-shot (M7680/M7700). When this one-shot times out, the
R/W /S Ready flip-flop sets to disable the Seek Incomplete counter, light the SEEK DONE/ON CYL
indicator, and generate the BUS RIW IS READY /L interface signal. The drive is now ready to perform a read, write, or another seek operation.
4.2.5.3 Reverse Seek - A reverse seek is similar to a forward seek (Paragraph 4.2.5.2); however, if the
current and new addresses are not alike, the subtractor (M7681/M7702) addition operation always
results in a carry condition. Because of this fact, the "not zero" decoding gate is not used during this
operation. The carry output from the subtractor sets the Reverse flip-flop to allow the Current
Address register to decrement.
NOTE
Because of unique timing considerations during the
reverse seek, inverted count pulses are used to decrement the Current Address register.

If during the initial power-on cycle, the heads are not fully retracted (unloaded), the "home" microswitch at the rear of the positioner is not depressed and the HOME L signal is high. HOME L is
ANDed with LOAD HEADS L (high, because the RUN/LOAD switch is in the RUN position) to
generate REV Hand MOVE L. Simultaneously, LOAD HEADS L sets the Difference register to a
low-velocity binary output, thereby retracting the heads at low speed to the home position. At this
position, the carriage contacts the home microswitch, causing the HOME L signal to go low and thus
remove REV H and MOVE L.
The heads would not normally be over the disk during the initial power-on cycle. Thus, this operation
ensures that the positioner will not move forward until the drive is placed in the run mode.
4.2.5.4 Return-to-Zero (Restore) Seek - To return the read/write heads to cylinder zero, the controller generates a BUS RESTORE L signal, transmits a Strobe pulse, and addresses the disk drive
(Paragraph 4.2.4). Reception of the Strobe pulse (M7680/M7700) generates the GOOD STROBE H
pulse. This pulse, ANDed with BUS RESTORE H, resets the Seek Incomplete latch to remove the
BUS SEEK INCOMPLETE L interface signal. BUS RESTORE H also sets the RTZ flip-flop
(M7681/M7702) to accomplish the following:
1.
2.
3.
4.

Clear the New Address register.
Clear the Current Address register.
Set the Reverse flip-flop.
Produce the R TZ L signal.

RTZ L resets the Seek Incomplete counter and prevents it from incrementing.
When the Reverse flip-flop sets, REV H and MOVE L are generated. REV H is applied to the servo
logic to place it in the velocity mode and initiate reverse head motion (Paragraph 4.3.1.1). MOVE L
resets the RIW IS Ready flip-flop (M7680/M7700) to accomplish the following:
1.
2.

Reset the RTZ flip-flop.
Set the Outer Limit Extender latch, which holds the New and Current registers at zero.

D
""",,,,,t th"" D """"""""" "'r'lrl " .. t th .. ~ n .. u,,,, .. rl fli1"\_fln1"\(l
.l,-"'>3"''' "11,,, .l,-",Y"'.>3'" U l l U >3"''' " •• '" .l V . H U . l U .l.l.lP-.l.lVP".

oJ.

When the Forward flip-flop sets, the heads begin to return toward cylinder zero. Just before the heads
reach cylinder zero, OUTER LIMIT H goes low. The next output pulse (COUNT PULSE REV H)
from the positioner transducer (Paragraph 4.3.2.1) resets the Forward flip-flop and thus removes
FWD H and MOVE L.
4-15

FWD H low places the servo logic in the detent mode (Paragraph 4.3.1.2), while MOVE L high
triggers the 6-ms Positioner Settle Delay one-shot (M7680/M7700). When the one-shot times out, the
R/W /S Ready flip-flop sets to disable the Seek Incomplete counter, light the ON CYL indicator, and
generate the BUS R/W /S READY L interface signal. R/W /S READY H also comes high at this time
to clear the Outer Limit Extender latch.

If, at any time during normal operation, the read/write heads reach the inner limit of the recording
disk, INNER LIMIT H (M7681/M7702) goes high and sets the RTZ and Seek Incomplete flip-flops to
initiate a return-to-zero seek automatically.

4.2.6 Sector /Index Pulse Generation
To read or record data with specific formats (e.g., data blocks) as well as to retrieve or store data at
designated areas (sectors) on the disk, a timing scheme related to the rotational position of the disk is
required. The SECTOR and INDEX pulses are used to accomplish this. These pulses are generated by
slots in the recording disk hub that pass through a groove in the sector transducer. There are 12 equally
spaced sector slots (16 slots for an RK8/E), which designate the 12 or 16 sectors on the disk. There is
also one uniquely spaced index slot on the disk to indicate the last sector (one complete revolution).
The sector transducer, located directly in front of the spindle, is an optical device that contains a lightemitting diode and a photosensor. As the recording disk rotates, the slots on the disk pass between the
light-emitting diode and the sensor, producing negative SECTOR/INDEX pulses (Figure 4-10).
Because both the SECTOR and INDEX pulses are produced from a single transducer, logic elements
on the M7680/M7700 are used to separate these two pulses and to encode the sector address.
During disk rotation, SECTOR/INDEX pulses from the disk trigger the Sector Timing Delay oneshot. The pulse width of this one-shot can be adjusted to compensate for different sector transducer
locations within various disk drives. Thus, when disk cartridges are interchanged, each data record is
properly located with respect to the associated SECTOR pulse. The trailing edge from the Sector
Timing one-shot triggers the Index/Sector one-shot to generate a 1-~s INDEX/SECTOR L pulse. The
trailing edge of this pulse in turn triggers the I-ms Index Separator one-shot. The output signals from
this one-shot are applied to decoding gates to separate the SECTOR pulses from the INDEX pulse. If
another slot has not passed the transducer, the SECTOR L signal is produced and the 4-stage Sector
Address counter is incremented. This sequence of events is repeated for every sector on the disk hub.
The occurrence of the last SECTOR pulse triggers the Index/Sector one-shot as before; however, 600
~s later the INDEX pulse from the disk hub retriggers this one-shot. The set output from this one-shot

is then ANDed with the set output from the Index Separator one-shot (still high from the previous
triggering) to generate the INDEX PULSE L signal and to set the Counter Reset flip-flop. The leading
edge of the next SECTOR pulse (sector 00) clears the Sector Address counter, and the trailing edge of
this pulse resets the Counter Reset flip-flop. Thus, for every revolution of the disk, the counter is
cleared to maintain the correct counter-to-disk relationship.

4.3

CARRIAGE POSITIONING

4.3.1 Positioner Servo Description
The positioner servo system (G938/G938Y A) controls the carriage movement. There are two control
loops within this system. A velocity loop controls the carriage velocity during a seek operation (velocity mode) and a position loop electronically detents the heads at a fixed cylinder location when a seek
operation is not being performed (detent mode). During the velocity mode, velocity and direction
commands are obtained from the cylinder address and difference logic (Paragraph 4.2.5). During the
detent mode, velocity and position feedback signals are derived from the linear positioner transducer
(Paragraph 4.3.2.1).

4-i6

SECT 10 (14)

SECT 11 (15) INDEX

x'oueER OUTPUT

SECT 00

U---------lf1j
I

----.t 600 JL S l4=-

I
I

SECTOR TIMING .l.
ONE-SHOT
r-! .
--+j
I+-ll0JLs(ADJUSTABLE)

I .-CI .-L
L.:J L..:r"

INDEX/SECTOR
ONE-SHOT

---'L...-.._ _ _ __

, . . . 1- ' -_ _ _ _ _ _ _ _ _ _' - - _ - - ' -_ _ _ _ _ _ _

SECTOR L~~---------__--_+---------~-------

INDEX SEPARATOR
ONE-SHOT

INDEXL~--------------_+~---------------___

I
I
COUNTER RESET

1 - - - - - - - - - - - - - - - - - - -.........

FLIP - FLOP

SECTOR
ADDRESSCOUNTERL...-..'--_ _ _ _ _ _ _ _ _~_ _+---------~------CNT=II(15)
CNT = to (14)
CNT=OO

~--------------~A~------------~
SECTOR L I~

__-\~ ~

NOTE: THE NUMBERS IN
PARENTHESIS ARE FOR
AN RKS/E SYSTEM.

INDEX SEPARATOR ~
ONE-SHOT
~

INOEXL~
I

r------1
f-I

COUNTER RESET I
FLIP-FLOP

SECTOR
ADDRESSCOUNTERIL...-..__________~____________

CNT=OO

)
CP-0261

4-17

The servo system (Figure 4-11) is composed of the following functional areas.
•

A linear positioner transducer that produces two sinusoidal signals. During the velocity
mode, these signals are used to control the rate of carriage movement. During the detent
mode, only one of these signals is used to electronically detent the carriage. In addition, the
transducer also generates two limit signals that indicate the extremities of carriage travel.

•

A velocity function generator that converts the digital difference signal into corresponding
analog velocity commands.

•

A velocity synthesizer that generates a feedback control signal from the transducer output.

INNER /OUTER LIMIT
COUNT PULSES

COUNT PULSE
GENERATOR
FWD/REV
POSITION
LOOP

CYLINDER
ADDRESS

ADDRESS
AND
CONTROL
LOGIC

DIGITAL
DIFFERENCE

VELOCITY
FUNCTION
GENERATOR

VELOCITY
COMMANDS

POSITIONER
AND
TRANSDUCER

VELOCITY
VELOCITY
LOOP
VELOCITY
SYNTHESIZER

SI N a COS
POSITION
CP-0509

Figure 4-11

Servo System Block Diagram

4.3.1.1 Velocity Mode - During a seek operation, the cylinder address and difference logic computes
the digital difference bet ..veen the present cylinder address and the destination cylinder (Paragraph
4.2.5). This digital difference is then converted, by the D / A velocity function generator of the analog,
to an analog velocity command. The amplitude of the analog signal depends upon the distance t{) the
destination cylinder. If the distance is greater than 31 cylinders (or 63 cylinders, in the case of an
RK05-F), a maximum velocity command is produced and applied to the velocity control loop. As the
carriage accelerates, a feedback velocity signal is generated by the velocity synthesizer. When a speed
of 35 ips is attained, this feedback signal inhibits further acceleration and maintains a constant 35 ips
carriage speed until the heads are 31 (or 63) cylinders from the destination cylinder. From this point,
the carriage decelerates at a controlled rate that is governed by the decrementing digital difference
applied to the function generator.

4-18

When the heads are 3 cylinders (7 cylinders in the case of an RKOS-F) away from the destination
cylinder, the velocity generator produces a fixed low-velocity command that continues to move the
carriage at low velocity (about 3 ips) until the heads are approximately one-half cylinder from the
destination cylinder. At this point, the low velocity command is removed; however, the velocity signal
remains to damp the carriage movement and prevent overshoot. Once the destination cylinder is
reached, the position loop electronically detents the carriage.
4.3.1.2 Detent Mode - The detent mode of operation electronically retains the read/write heads at a
desired cylinder with a force greater than 2000 pounds per inch. During this operational mode, the
velocity command from the function generator is zero, allowing the small velocity feedback signal to
produce a stable position loop. If the heads tend to deviate from the desired cylinder, an error correction signal (SIN POSITION), which is opposite in polarity from the direction of deviation, is generated by the positioner transducer. This error signal is then directly applied through the loop amplifiers
to move the carriage back to the desired cylinder.
4.3.2

Servo Circuit Description

4.3.2.1 Linear Positioner Transducer - The positioner transducer (Figure 4-12), located on the underside of the carriage, is an optical device that consists of two parts. The stationary portion (reticle) of
the transducer is constructed in a U shape and is attached to the carriage slide. One side of the U
contains a lamp; the other side contains a stationary reticle with minute diagonal transparent slots,
plus six photosensors located behind the slots. The movable portion (scale) of the transducer contains
a similar section of minute vertical transparent slots and is attached to the movable carriage. As the
scale moves in the middle of the U-shaped reticle, the vertical and diagonal slots allow varying light
patterns to shine onto the photosensors. This action produces two sine wave output signals that occur
90 degrees out of phase. These signals (SIN POSITION and COS POSITION) are used to control the
movement of the carriage.
Two dc signals (INNER LIMIT and OUTER LIMIT) are also generated by the transducer. As long as
the scale travel remains within the slotted section (cylinder 0 through 202), neither one of these signals
is produced; however, when the scale reaches the inner travel extremity (> cylinder 202 for RKOS,
RKOS-J, and the odd drives of RKOS-F), the inner limit photosensor is uncovered and the negative
INNER LIMIT signal is produced. The positive OUTER LIMIT signal is produced in a similar
manner at the outer travel extremity « cylinder 0 for RKOS, RKOS-J, and the even drive of RKOS-F).
4.3.2.2 Velocity Function Generator - The velocity function generator (Figure 4-13) is as-bit D / A
converter. The generator logic elements are located on the G938/G938Y A card. The S-bit digital input
to this logic component is derived from the five low-order difference bits from the cylinder address and
difference logic. During a seek operation, these five bits represent the distance from the present cylinder address to the destination cylinder (Paragraph 4.2.S). If this distance is greater than 31 in the
RKOS/RKOS-J or 63 in the RKOS-F, aIlS input bits are low, producing a maximum amplitUde output
signal (velocity command). If the travel distance is less than or equal to 3 for the RKOS /RKOS-J or 7
for the RKOS-F, all S inputs are high, producing a minimum velocity command. For differences
between 4 and 30 for the RK05/RK05=J or bet\veen 8 and 62 for the RK05-F, the velocity command is
proportional to the S-bit binary representation. The velocity command is connected by Field Effect
Transistors (FETS) to the summing node of the loop amplifier. To initiate carriage motion, the FWD
or REV signal turns on the appropriate FET, thereby applying the velocity and direction command to
the loop amplifier.
4.3.2.3 Velocity Synthesizer - In a closed-loop servo system, a speed-sensing feedback control signal
is required to prevent uncontrolled velocity within the system. In the drives that comprise the RKOS
family, this control or tachometer signal is electronically derived in the velocity synthesizer. These
elements are located on the G938/G938Y A card.

4-19

HEAD
SUSPENSION
ARM

CARRIAGE

STATIONARY RETICLE
(PHOTO SENSORS BEHIND)---t---i---;i--T'l~\
POSITION
TRANSDUCER

CP-0262

Figure 4-12 Linear Positioner Transducer

4-20

FWD

CYLINDER
DIFFERENCE

VELOCITY
FUNCTION
GENERATOR

>----'-------+TO POSITIONER DRIVER
LOOP AMPLIFIER

REV
POSITION

VELOCITY

SQUARING
AMPLIFIERS

DECODER-

SIN POS
AMPLI FIERS
AND
I NV E RTE RS 1---.JVI.fIv------,----1

1------1

SELECTOR

COS POS

______4_Ll_N_E_S--+lDIFFERENTIATORS
CP-0510

Figure 4-13

Simplified Positioner Servo Logic

During a seek operation, the SIN POSITION and COS POSITION signals from the positioner transducer are applied to amplifiers and unity gain inverters to provide four phases of position signal at the
input of the synthesizer. The inverter/amplifier outputs are also applied to four differentiator networks. Appropriate pairs of amplifier/inverter outputs are applied to the summing junctions of two
squaring amplifiers. The resultant square wave signals are displaced 90 degrees from each other and
when these signals are gated together in the decoder/selector, they produce four separate selection
signals of 90-degree duration. Each selection signal is centered around the peak of the corresponding
differentiated signal. The derivative signals are then selectively summed in an operational amplifier to
produce the velocity feedback signal. This signal is then applied, through a gain-setting resistor, to the
summing node of the loop amplifier. Here, the velocity command from the velocity function generator
is summed with the velocity feedback signal to produce a velocity profile signal (Figure 4-14 reflects
the velocity profile for the RK05/RK05-J). Thus, for a 202-cylinder seek (full carriage stroke in the
RK05/RK05-J), a maximum velocity profile is produced. The dotted lines in Figure 4-14 represent the
initial portions of shorter seeks; however, the terminating portion of all seeks remains the same.
During the detent mode of operation, the POS signal turns on an FET that applies the SIN POSITION
signal directly to the summing node of the loop amplifiers. This circuit configuration retains the heads
at the desired cylinder location.

4-21

31 CYLINDERS TO GO

3CYUNDERS TOGO
200CYUNOERSTO GO ~
DETENT MODE

Figure 4-14

Velocity Profile (RK05/RK05-J)

4.4 READ /WRITE
All the circuit elements required for head selection, level changing, and waveform shaping during a
read/write operation are on the G 180 card, which is located in the first position of the electronic
module. The read/rite head connectors are directly attached, through an opening in the side of the
electronic module, to connector pins on this card.
4.4.1 Read Operation
During a read operation, the selected read/write head detects flux reversals from a recorded data track
on the rotating disk. Each flux reversal generates a small voltage peak, whose polarity corresponds to
the direction of the flux reversal. The read waveform is then amplified, filtered to remove high-frequency noise components, and applied to wave-shaping circuits. These circuits convert each voltage
peak to 160-ns logic level pulses and apply this pulse train to the data separator circuits (Figure 4-15).
In the separator, the individual data and clock pulses are separated according to the double-frequency
recording scheme (Paragraph 4.1.4). The data separator also contains frequency tracking and peakshift compensating circuits.
Figure 4-16 shows the time relationship and the waveforms for a read operation. The letters in parentheses ( ) in the following text correspond to the lettered waveforms in the figure.
To initiate a read operation, the controller:
1.
2.
3.

Addresses a particular drive (Paragraph 4.2.4).
Positions the read/write heads at the appropriate cylinder (Paragraph 4.2.5).
Selects either the upper or lower read/write head (Paragraph 3.2.5).

For example, if the lower read/write head is to be used, the signal HD SELECT (G 180-0-1) is high.
This signal is ANDed with UNSAFE L (high, if no fault condition exists, Paragraph 4.5) to apply a
ground potential to the center tap of the lower head.

4-22

CLOCK

DATA GATE
READ
DATA H

a DATA
+3

INTEGRATOR

DATA
WINDOW

CLOCK GATE

7474

READ
CLOCK H

CLOCK L
F

WINDOW
CONTROL
ONE-SHOT
9601
420ns

DATA L

DATA ONE
WINDOW
DELAY

L....---IC 7474

E4
CP-0508

Figure 4-15

Simplified Data Separator Circuit

4-23

fA)

READ SIGNAL famplified)

fB)

DIFFERENTIATED

fC)

COMPARATOR

'CD)

CLOCK & DATA TRAIN

i
(E)

DATA ONE WINDOW DELAY

(F)

WINDOW CONTROL ONE-SHOT

fG)

DATA WINDOW

fH)

CLOCK L

DATA L

X
Y

Figure 4-16

DELAY FOLLOWING ZERO
NO DELAY FOLLOWING ONE

Read Waveforms

4-24

As flux reversals on the disk surface pass under the lower read head, induced current flows through the
lower head coil. Jhe direction of this current flow depends upon the polarity of the flux reversal. These
small read signals' (approximately 5 m V) are then transmitted through the head-select diodes, through
the series-isolation diodes, to a differential read preamplifier. The diode, resistor, and capacitive network between the read/write coils and the read preamplifier automatically isolates the preamplifier
from the large write signals that occur during a write operation; however, this isolation circuit allows
the small read signals that occur during a read operation to pass.
The amplified output from the preamplifier (approximately 300 mY) is then transmitted through a
low-pass filter network to the read amplifier. The filter network removes noise and high-frequency
disturbance but permits the lower frequency read signals to pass. The approximate 3.0 V read amplifier
output (A) is applied to a balanced delay circuit where the signal is differentiated (B) and the signal
peaks converted into zero crossings. The complementary zero crossings are then applied to a pair of
high-gain differential comparators that convert the differentiated signal into square waves. Each
square wave signal (C) triggers a corresponding one-shot, the outputs of which are combined to produce a composite 150-ns pulse train (D).
At this point, data and clock pulses are separated from the pulse train. Figure 4-15 is a simplified
diagram of the data separation circuit. For a basic understanding of the following description; assume
that the Data One Window Delay flip-flop remains set, keeping the input gate of the Window Control
one-shot enabled.
I f the Data Window flip-flop is in the reset state (G) when the leading edge of the first pulse on the
pulse train occurs, the clock gate (E3) is enabled to produce the BUS RD CLK L signal (H) and to
trigger the Window Control one-shot (F). The reset output from this one-shot is applied to an
integrator circuit. After integration, the average voltage output is then applied to the adjustable input
of the one-shot. Thus, if data frequency variations occur, this circuit configuration automatically
varies the one-shot pulse width and thus maintains a constant duty cycle.
Triggering the Window Control one-shot also removes the reset input of the Data Window flip-flop so
that the trailing edge of the first clock pulse will clock the Data Window flip-flop set. Approximately
290 ris after this sets (slightly more than one-half bit cell), the Window Control one-shot will time out.
If another pulse occurs on the pulse train (data 1 bit) before the time out, it will be enabled in the Data
Gate (E2) to produce BUS RD DATA L (I), which will also keep the Data Window reset gate (EI)
disabled for the duration of the data pulse so that the Data Window flip-flop will not be reset during
the data pulse by the one-shot time out.
If another pulse did not occur (data 0 bit), the Data Window flip-flop will be reset by the one-shot time
out via the Data Window reset gate.
In some bit sequences (e.g., a data 1 following a data 0), it is desirable to delay the resetting of the Data
Window slightly longer than the normal one-shot time out. A magnetic recording phenomenon known
as peak shift can cause the data 1 bit to lie beyond the cell center. A delaying circuit is provided so that
whenever a data 0 bit occurs, reset of the following Data \Vindow flip=flop is delayed, regardless of
what the following data bit may be.
To accomplish this, a Data One Window Delay flip-flop set output is used to enable the Window
Control one-shot.

4-25

The occurrence of a data 1 pulse direct-sets the Data One Window Delay flip-flop. The set output (E)
then provides an enable signal to the Window Control one-shot so that the next clock pulse triggers the
one-shot without delay. If a data bit is 0, the Data One Window Delay is not set until the leading edge
of the following clock pulse. The set output rise is slowed by capacitor C 1. This slow rise, gated with
BUS RD CLK L, prevents the immediate firing of the one-shot, thus delaying the Data Window flipflop reset. The one-shot firing also resets the Data One Window Delay via its reset gate (E4). This
allows the Data One Window Delay flip-flop to be set by a possible data 1 pUlse.
4.4.2 Write Operation
During a write operation, multiplexed write data and clock pulses are applied to the complementary
Write Encode flip-flop. If the Write Gate signal is present and one of the read/write heads has been
selected, current flows through the erase coil as well as through one-half of the center-tapped write
coil. Each pulse on the multiplexed input complements the Write Encode flip-flop and transfers current flow to the opposite half of the write coil; however, current flow through the erase coil remains
constant throughout the write operation.
To initiate a write operation, the controller:
I.

2.
3.

Addresses a particular drive (Paragraph 4.2.4).
Positions the read/write heads at the appropriate cylinder (Paragraph 4.2.5).
Selects either the upper or lower read/write head (Paragraph 3.2.5).

For example, if the lower read/write head is to be used, HD SELECT (G 180-0-1) is high. This signal is
ANDed with UNSAFE L (high, if no fault condition exists, Paragraph 4.5) to apply a ground potential to the center tap of the lower head.
At this point, the controller transmits the BUS WT GATE L signa!, which is .A~NDed with
SELECT /READY L to generate the signal SELECTED WRITE GATE H. The multiplexed data to
be recorded is then transmitted over the BUS WT DATA & CLK L interface line. If the WT PROT
switch is off (drive not write-protected), the signal NO PROTECT L accomplishes the following:
l.

ANDs with BUS R/W IS READY/ON CYL L to complete the base current return circuit
for the write drivers (Ql and Q2).

ANDs with BUS WT DATA & CLK L to apply the data train to the complementary Write
Encode flip-flop.
NOTE
The Write Encode flip-flop operates between +10 V
and + 15 V instead of the usual ground and +5 V
levels.

When the BUS WRITE DATA & CLOCK pulse goes low, the Write Encode flip-flop sets, applying
the + 10 V reset output to the base of write driver Q2, causing it to conduct. With Q2 conducting,
approximately 32 rnA of current (adjustable with R 13) flows through the upper portion of the lower
write coil. In addition, a low voltage is -applied to the base of the Erase Current Switch (Q3), causing it
to conduct. When Q3 conducts, one leg of the Unsafe gate is enabled (Paragraph 4.5.1) and erase
current flows through the lower erase coil.
When the BUS WRITE DATA & CLOCK pulse goes low again, the Write Encode flip-flop resets,
causing write driver QI to conduct and Q2 to cut off. This circuit configuration transfers the current
path to the lower portion of the lower write coil; however, the current direction in the erase coil
remains constant. Thus, with each current transfer in the head coil; a flux reversal is recorded on the
rotating disk surface.
4-26

4.5 FAULT DETECTION
If during normal operation the following three fault conditions are detected, all external commands to
the drive are suppressed and the FAULT indicator on the drive control panel lights. The fault conditions are:
1.
2.
3.

Erase or write current without a BUS WT GATE L signal.
Linear positioner transducer lamp inoperative.
Any or all of +15, -15, or +5 Vdc low (dc low).

4.5.1 Current Fault
During a write operation, write driver Q 1 or Q2 (G 180-0-1), depending upon the polarity of the input
data, is conducting. The low voltage output from either write driver turns on Erase Current Switch Q3
to enable one leg of the Unsafe gate. If BUS WT GATE L is present, the second leg of this gate is
disabled; thus, Q4 conducts to keep the signal SET UNSAFE L high.
If for any reason (e.g., shorted transistor), the Erase Current Switch should conduct without a BUS
WT G ATE L signal present, the Unsafe gate is enabled. This action turns off Q4 to generate SET
UNSAFE L, which accomplishes the following:
1.

2.
3.

Sets the Fault latch (M770I).
Generates the BUS WT CHK L signal and lights the FAULT indicator (M7701).
Deselects both read / write heads (G 180-0-1).

4.5.2 Positioner Lamp Fault
This fault condition can only be detected when the read/write heads are in the home position. If the
positioner lamp fails at any other time, various other checks will disclose this fact (e.g., BUS SIN L
generated or BUS R/W /S READY L never generated, etc.). Therefore, the positioner lamp check is
accomplished during the initial power-on cycle, or if the heads drift back to the home position after
having once been loaded.
If the lamp fails and the heads are in the home position, HOME H (M770I) is present; however,
OUTER LIMIT H (heads are at or beyond the outer portion of the disk) is low. This signal combination sets the Fault latch to light the FAULT indicator and generate the BUS WT CLK L signal.

4.6 POWER SUPPLY DESCRIPTION (Figure 4-17)
The RK05 Disk Drive power supply (H743) and associated electronic cards are located in the left-rear
portion of the disk drive. The power supply itself can be operated from a 115 or 230 Vac line voltage
input, and consists of a dual transformer, two bridge rectifiers, and three voltage regulators. For 115
Vac operation, jumpers between P2 pins 1 and 2 and P2 pins 3 and 4 connect the dual primaries of
transformer TI in parallel. For 230 Vac operation, one jumper between P2 pins 2 and 3 connects the
dual primaries of transformer T1 in series, thus maintaining 115 Vac across each primary. In either
configuration, the 115 Vac blower motor is connected across T1 pins 1 and 2, while the 115 Vac spindle
motor is connected across T1 pins 3 and 4.
When the power supply is activated, the secondary output of T 1 pins 7 and 8 is applied through fullwave bridge rectifier D2, across capacitor C2, to the input of both the + 15 V and + 5 V regulators. The
other Ti secondary output is likewise applied through fuii-wave bridge rectifier D i, across capacitor
C1, to the input of the -15 V regulator. The regulator outputs are maintained within the following
specified voltage limits, measured to center value of the peak-to-peak ripple from ground:
1.

2.
3.

+ 15 ±0.75 Vdc
-IS ±O.75 Vdc {
+5 ±0.15 Vdc ,

200 m V peak-to-peak maximum ripple on any of the regulators,
and 250 m V peak-to-peak maximum rip pie on dc voitage pins
of the logic assembly

All three regulators contain current-limiting circuitry and are further protected against short circuits
by a permanent fuse. Only the + 5 Vdc regulator (logic power) contains a nonadjustable Zener diode
for automatic overvoltage protection.
4-27

6858·3

Figure 4-17

Internal Power Supply Connections

4-28

CHAPTER 5
MAINTENANCE

5.1 CUSTOMER EQUIPMENT CARE
Because the cartridge is not a sealed unit and is extremely vulnerable to dirt, care must be taken to keep
the cartridge and the interior of the drive clean. Smoke particles, fingerprint smudges, or dust specks
can cause head crashes and catastrophic destruction of the heads and disk surfaces, as Figure 1-12
shows. For this reason, there are practices and procedures that the customer can follow which should
contribute to the performance and longevity of the RK05.
5.1.1 Weekly Care
Every week (or more frequently, depending upon activity) the customer should:
1. Clean the front window of the drive, using a lint-free wipe or cloth moistened with glass
cleaner.

2. Remove any accumulated dust buildup from the front panel, using a dry, lint-free wipe or
cloth.
5.1.2 Monthly Care
Every month (or more frequently, depending upon activity) the customer should:

1. Inspect the interior of disk cartridges for visible dirt or damage.
2. Check that cartridge doors close properly.
3. Check that cartridge air vent door rivets are not broken.
4.

Check that retainer buttons on the bottom of cartridges are not being chewed up; this could
cause plastic shavings to fall into cartridges.

Remove any dust or dirt from the exterior of cartridges, using a lint-free wipe or cloth
dampened with water.

Vacuum the outer face oftne prefilter (Figure 5-1). if there is excessive dirt on the prefilter,
remove the filter and clean it with a mild liquid detergent and warm water. Using the
exhaust of the vacuum cleaner, air-dry the filter completely before reinstalling it.

5.2 PREVENTIVE MAINTENANCE
Information regarding preventive maintenance of the RK05/RK05-J /RK05-F Disk Drives is contained in the following publications:
RKOS/RKOS-J Disk Drive Preventive Maintenance Procedures (EK-RK05J-PM-001)
RKOS-F Disk Drive Preventive Maintenance Procedures (EK-RK05F-PM-001)

5-1

SCREWS

6474-4

Figure 5-1

5-2

Prefilter

Table 5-1 lists the recommended tools and test equipment to be used with standard tools for proper
maintenance of the RK05/RK05-J/RK05-F Disk Drive. During the PM procedures, do not alter any
adjustments on drives that are performing within specifications, unless specifically indicated.
Table 5-1

Recommended Tools and Test Equipment

Equipment

Manufacturer and Model/Part No.

Multimeter
Oscilloscope
Oscilloscope probes, voltage
Screwdriver, Phillips, small
Wire wrap tool (30-gauge)
Unwrapping tool (30-gauge)
Module Extender Board*
Wrench set (10-piece)
Torque wrench assembly, 55 oz-inch
(for old head clamping screws)
Torque wrench tip, 55 oz-inch
Torque wrench assembly, 125 oz-inch
(for new head clamping screws)
Torque wrench tip, 3/32 inch Allen
Extension bar, 6-inch
Hex-head wrench, 3/16-inch
Head-cleaning kit
includes Tex pads (29-19557)
and wand (29-19558)
I nspection mirror
Isopropyl alcohol, one pint (91%)
Alignment cartridge
Spring hook, teletypewriter

Triplett 310, or Simpson 360
Tektronix 453, or equivalent
Tektronix P60 10
Vaco P-l, or equivalent
DEC H811A
DECH812A
DECH982
29-13519
29-20994
29-20995
29-22521
29-22522
29-20907
29-20908
22-00007
29-19663
29-19665
RK05-AC
29-12528

*N ot to be used for G 180 module.

5.3

CORRECTIVE MAINTENANCE

5.3.1
5.3.1.1

Linear Positioner
Positioner Removal
NOTE
Before removing wires, check that they conform to
the configuration indicated on the wire replacement
chart (Table 5-2).
CAUTION
Bumping of the positioner on the haseplate or locating pins may raise burrs that will severely mislocate
the positioner upon reinstallation.

5-3

Table 5-2 Positioner Transducer Wire Configuration

•
•
•
•
•
•
•
•
•

Green/\Vhite
White/Black
Green/Black
Blue/White
Blue
Blue/Black
Black/White
Orange/White
Black

Blue
Yellow
Green
Orange
Gray
Brown
Red
White }
White

Reference - +5 V dc
to linear encoder lamp

Remove the disk cartridge from the drive.

Open the rear door of the rack and unplug the drive ac line cord.

3. Slide the drive out of the rack until it locks in the extended position.
4.

Remove the top and bottom covers.

Remove the read/write heads as described in Paragraph 5.3.3.2.

Install the linear motor (positioner) shipping bracket.

Disconnect P5 (Figure 4-17) from the power supply chassis.

Remove the positioner transducer wires from TBI pins 1 through 9, and from TB2 pins 8
and 9. Note the order, to aid in replacement.

Disconnect the head connectors from the electronic module (G 180).

10.

Remove the three screws beneath the baseplate that attach the positioner to the baseplate
(Figure 5-2).

11. Carefully maneuver the positioner off the locating pins on top of the baseplate, and lift the
positioner straight up from the baseplate.
"i.~.1. '2

Positioner Replacement
1. Carefully place the positioner on the three locating pins on top of the baseplate. Ensure that
the two front pins rest against the front surface of the motor housing and the third diamondshaped pin is in the center hole of the mounting face.

Insert the three positioner holding screws (Figure 5-2) through the bottom of the baseplate
and finger-tighten the screws.

Ensure that the positioner is located securely against the front locating pins by tightening the
holding screws with a torque wrench (set to 65 pound-inches) while applying forward pressure to the rear of the positioner.

5-4

RECESS

POSITIONER SCREWS

AIR
INTAKE

AIR
EXHAUST

ABSOLUTE FILTER

Figure 5-2

BLOWER OUTLET

Absolute Filter Removal

4. With a feeler gauge, ensure that clearance between the front of the linear motor housing and
the two front pins is less than 0.002 inch. If not, loosen the positioner holding screws and
repeat Step 3, above.
5. Connect the positioner transducer wires to TBI and TB2 (Figure 5-3).

NOTE
Refer to the chassis wiring diagram for TBI and TB2
connection color code.
6.

Remove the linear motor (positioner) shipping bracket.

Plug P5 (Figure 4-17) into the power supply chassis.

Replace the read/write heads as described in Paragraph 5.3.3.3.

9. Connect the head leads to the electronic module (G 180). (Refer to the pin number decal on
the logic assembly and to schematic CS-G 180 for plug locations.)
10. Connect the ac line cord and check read/write head alignment (Paragraph 5.4.5).
11.

Replace the bottom covers, and then replace the top cover.

5-5

HEAD
CONNECTOR

READ/WRITE

BEARING TIRE

HOUSING

FLEXSTRIP
CONNECTOR
SCREWS

MOTOR
HOUSING

READIWRITE
HEADS

CABLE
CLAMP
CARRIAGE
SLIDE

BATTERIES

FLEXSTRIP
HOLDDOWN
SCREWS

ARMATURE

FLEXSTRIP
COUPLING

FLEXSTRIP

CARRIAGE

6858-5

Top View of RK05 with Cover Removed

12. Close the rear door, install a test cartridge, and exercise the drive.

NOTE
The top head should connect to the pins farthest from the logic block.
5.3.2

Carriage

5.3.2.1

Carriage Removal

1. Remove the linear positioner (Paragraph 5.3.1.1).
2.

Remove the read/write heads (Paragraph 5.3.3.2).

Remove the four flexstrip connector and flexstrip hold-down screws (Figure 5-3). Do not
disconnect the flexstrip coupling from the armature.

Remove the cable clamp screw from the top of the motor housing.

Remove the home switch and bracket from the carriage slide.

Remove the five screws securing the carriage slide to the motor housing.

Slowly pull the carriage and slide straight out from the motor housing.

5-6

8. Slide the carriage and armature out from the back of the carriage slide, ensuring that the
transducer block does not contact the glass scale.
5.3.2.2

Carriage Replacement

1. Carefully insert the armature and carriage into the motor housing, ensuring that the dowel
pin on the housing goes into the V-groove on the carriage slide.
2.

Replace the five screws that secure the carriage slide to the motor housing (Figure 5-3).

Loop the flexstrip onto the top of the motor housing and replace the four flexstrip connector
and hold-down screws.

4. Replace the cable clamp.
5.

Replace the home switch and bracket on the carriage slide.

Stand the positioner up on the motor housing end; adjust the home switch as follows:
a.

Pull the carriage out from the motor housing until the switch actuator on the carriage is
free from the switch.

Hold a steel scale across the machined face of the carriage slide and stand another scale
on the machined face (near the head mounting holes) of the carriage.

Slowly move the carriage in toward the motor housing until the home switch clicks. At
this point, the vertical steel scale on the carriage face should indicate 2.050 ± 0.020
inches.
NOTE
The switch check and adjustment must be made on
the backward click of the home switch, NOT while
the carriage is moving forward.

d.
7.

If the switch adjustment is incorrect, bend the leaf actuator on the switch until the
measurement from Step c, above, is attained.

Replace the read/write heads (Paragraph 5.3.3.3).

8. With a piece of blue plastic shim stock, check for O.005-inch clearance between the transducer glass scale and reticle. If the clearance is incorrect, loosen the transducer block mounting screws and position the block to obtain the correct clearance.

NOTE
Do not lose the front-to-back position obtained in
Step 6. Reference lines may be drawn on the slide
before the block is loosened.
9.

Replace ihe linear posiiioner (Paragraph 5.3. i,2).

10. Perform the servo system timing adjustment (Paragraph 5.4.2).
11. Check the read/write head alignment (Paragraph 5.4.5).

5-7

5.3.2.3

Carriage Bearing Assembly Removal
1.

Remove the linear positioner (Paragraph 5.3.1.1).

2. Remove the carriage from the linear positioner (Paragraph 5.3.2.1).
3.

Using a 3/8-inch nut driver, loosen the bearing shaft nut (Figure 5-4) one-half turn.

Hold the 3/8-inch bearing shaft nut and remove the retaining nut from the other end of the
shaft.

Remove the bushing from the shaft and unscrew the bearing shaft.

Remove the bearing.

NOTE
Replace all four bearings at the same time.

WIDE
MACHINED
SURFACE

1·---.53
....

Figure 5-4

Carriage Bearing Assembly Removal

5-8

5.3.2.4

Carriage Bearing Assembly Replacement
1.

Examine the bearing (P /N 12-11475) for a groove running around the outer diameter of the
tire. If the groove is absent (Figure 5-4a), insert the bearing into the bearing pocket with the
widest machined surface of the bearing toward the threaded hole in the pocket. If the groove
is present (Figure 5-4b), insert the bearing into the bearing pocket with the groove nearest
the threaded hole.

Insert the bearing shaft into the threaded pocket hole and through the center hole in the
bearing.

Turn the 3/8-inch bearing shaft nut just a few turns to start the shaft threads into the pocket
hold threads. Do not tighten the shaft at this time.

Insert the bushing on the other end of the shaft and replace the retaining nut.

NOTE
When performing Steps 5 and 6, do not allow the
bearing assembly to touch the top or bottom of the
carriage pocket.
5.

Hold the 3/8-inch bearing shaft nut and tighten the retaining nut until the bushing moves
the bearing close to the pocket top. Then tighten the 3/8-inch bearing shaft nut until the
bearing moves close to the pocket bottom.

6. Continue alternate nut tightening as described in Step 5, above, until the bearing shaft and
retaining nuts are secure.
7.

Replace the carriage in the linear positioner (Paragraph 5.3.2.2).

Replace the linear positioner (Paragraph 5.3.1.2).

Check the read/write head alignment (Paragraph 5.4.5).

5.3.2.5

Transducer Block Removal and Replacement
1.

Remove the linear positioner (Paragraph 5.3.1.1).

Remove the clamp attaching the positioner transducer leads to the carriage slide.

Remove the two screws attaching the transducer block to the carriage slide and carefully
maneuver the transducer block out of the slide, ensuring that the block does not scratch the
glass scale.

Install the new transducer block on the carriage slide with the previously removed hardware.

Replace the transducer leads in the clamp and attach the clamp to the carriage slide.

With a piece of blue plastic shim stock, ensure that the clearance between the transducer
glass scale and the reticle is 0.005 inch. If the clearance is incorrect, loosen the transducer
block mounting screws and reposition the block to obtain the correct clearance.

Replace the linear positioner (Paragraph 5.3.1.2) and perform the servo system timing
adjustment (Paragraph 5.4.2).

Align the read/write heads (Paragraph 5.4.5).
5-9

5.3.2.6 Transducer Bulb Replacement - Burned-out transducer bulbs may be replaced without disassembly of the transducer block from the positioner by using lamp assembly 30-10636-03 and clamp
assembly 70-12691-0-0.
5.3.3

Read/Write Heads

5.3.3.1 Carriage Revisions - Older carriages employ conical-tipped head-clamping screws that bear
on the facets on the side of the support arm. These set screws are to be driven with a hex screw bit (2920995) mounted in a torque wrench set at 55 ounce-inches of torque (Figure 5-5a).
Newer carriages employ brass-tipped clamping screws that bear on the solid diameter of the support
arm. These set screws are to be set with a hex screw bit (29-22522) mounted in a torque wrench set at
128 ounce-inches of torque (Figure 5-5b).
5.3.3.2

Head Removal

Remove the disk cartridge from the drive.

2. Open the rear door of the rack and unplug the drive ac line cord.
3. Slide the drive out of the rack until it locks in the extended position.
4.

Remove the top cover.

Disconnect the head connectors (Figure 5-3) from the electronic module.

Disconnect P5 (Figure 4-17) from the power supply chassis.

Remove the head clamp and head adjusting screws.

Retract the carriage to unload the heads and carefully remove the upper head (Figure 5-6a).

Extend the carriage and remove the lower head (Figure 5-6b).

5.3.3.3

Head Replacement

Extend the carriage and insert the lower head tailpiece into the carriage (Figure 5-6b).

Retract the carriage to the home position so that the lower head is supported by the lifting
block on the duckbill.

To install the upper head, it is necessary to straighten the head from its natural position.
Carefully install the upper head as follows:
a.

Insert the end of the tailpiece slightly into the carriage hole (Figure 5-6a).
CAUTION
Exercise extreme care while performing Step b,
below. If the yield point of the spring is exceeded
during the straightening process, the loading force on
the head will change.

5-10

OLD STYLE R!W
HEAD CLAMPS

6858-5

(a) Older Style Carriage
NEW STY!-E R!W HEAD
CLAMP SCREWS

7854-2

(b) Newer Style Carriage (RK05-F Shown - No Cartridge Receiver)
Figure 5-5

Read/Write Head Carriage Revision
5-11

CARRIAGE (HELD RETRACTED)

UPPER HEAD
TAIL PIECE

CLAMP SCREW
HOLES

ADJUSTING
SCREW HOLES

(a) Upper Head Removal and Installation
CLAMP

LOWER HEAD

LOWER HEAD
TAIL PIECE

CARRIAGE
HELD EXTENDED

(b) Lower Head Removal and Installation
Figure 5-6

Read/\Vrite Head Repiacement

5-12

Simultaneously press down at the front of the tailpiece and lift the front of the suspension spring while pushing the head backward. This process tends to straighten the head
suspension spring for easier insertion into the carriage hole. Do not over-bend the
suspension spring, and avoid touching the ceramic surfaces of the head pads during
installation.

Replace the head clamp and adjusting screws (Figure 5-6a) and using the appropriate torque
wrench (Paragraph 5.3.3.1), tighten the clamp screws with the heads located approximately
O.030-inch from the fully-seated position.

Replace the read/write head cables in the clamp on the carriage slide and connect the head
connectors to the electronic module. Refer to the decal on the chassis for the correct lead
connections.

Plug P5 into the power supply chassis.

Check the read/write head alignment (Paragraph 5.4.5).

Perform the index/sector timing adjustment (Paragraph 5.4.4).

Replace the top cover.

10. Close the rear door.
5.3.4

Spindle

5.3.4.1

Spindle Removal
CAUTION
Any bumping of the spindle on the baseplate may
raise burrs that will severely mislocate the spindle
upon reinstallation.

1. Remove the disk cartridge from the drive.
2.

Open the rear door of the rack and unplug the drive ac line cord.

3. Slide the drive out of the rack until it locks in the extended position.

Remove the top and bottom covers.

5. If a cartridge receiver is present, remove the tension springs from the cartridge receiver
(Figure 5-7) and raise the receiver as high as possible.
6.

Remove the flexible magnet from the spindle armature to expose the access hole in the
spindle plate.

Position the access hole over each of the spindle retaining screws and remove them. Do not
apply any force to the spindle armature plate (O.OOOI50-inch runout).

Lift the spindle free from the drive baseplate.

5-13

SPINDLE
CARTRIDGE
RECEIVER

TENSION
SPRING

SPINDLE MOUNTING
SCREWS (3 PLACES)

6858-8

Figure 5-7

Spindle Replacement

5.3.4.2

1. If a cartridge receiver is present, raise the cartridge receiver as high as possible and install the
spindle on the baseplate with the previously removed hardware. Avoid damaging either the
baseplate mounting surfaces or the spindle flange; this could cause the spindle to seat as
much as several thousandths of an inch out of its proper position.
2.

Lower the cartridge receiver and attach the tension spring (Figure 5-7).

Push the spindle motor mounting plate (Figure 5-8) tot-yard the spindle aD.d slip the dri';e
belt around the pulleys.

Connect the ac line cord and check the read/write head alignment (Paragraph 5.4.5).

Replace the top and bottom covers.

Slide the drive into the rack and close the rear door.

5-14

SPINDLE PULLEY

DRIVE BELT

SPINDLE MOTOR
PULLEY

- r..........-

CIRCUIT CARDS

SPINDLE MOTOR
RELAY

MOTOR MOUNTING
SCREWS

Figure 5-8

5.3.4.3

MOUNTING PLATE

Drive Belt

Spindle Ground (Carbon Brush) Removal and Replacement

1. Open the rear door of the rack and unplug the drive ac line cord.
2. Slide the drive out of the rack until it locks in the extended position.
3. Remove the bottom covers and remove the two screws that attach the carbon brush assembly to the spindle (Figure 5-9).
4.

Mount the new brush assembly on the spindle and ensure that the curved brushes are centered on the spindle hub and that the brush assembly is not cocked or twisted. Full contact
between the curved surfaces of the brushes and shaft is necessary to prevent brushes from
squealing.

5. Tighten the brush assembly mounting screws and replace the bottom covers.
6.

Slide the drive into the rack, reconnect the ac line cord, and close the rear door.

5.3.5

Spindle Drive Motor

5.3.5.1

Motor Removal

Remove the disk cartridge from the drive.

2. Open the rear door of the rack and unplug the drive ac line cord.

5-15

FOR 50 Hz OPERATION
MOVE MOTOR MOUNTING
SCREWS TO THESE HOLES (4)

MOTOR MOUNTING SCREWS (4)
(SHOWN FOR 60 Hz OPERATION)

Figure 5-9

CARBON BRUSH ASSEMBLY
MOUNTING SCREWS

CARBON BRUSH
ASSEMBLY

SPINDLE PULLEY

Carbon Brush Replacement

3. Slide the drive out of the rack until it locks in the extended position.
4.

Remove the top and bottom covers.

5. Disconnect the spindle motor leads from TB4 (Figure 5-3) and from the spindle motor relay
(Figure 5-8).
6.

Remove the drive belt (Figure 5-8) by pushing the spindle motor mounting plate toward the
spindle to relieve belt tension, and then slipping the belt off the pUlleys.
NOTE
The spindle motor mounting plate contains two sets
of holes, one for 50-Hz operation, the other for 60Hz operation. Before performing Step 7, below, note
which set of holes is being used, to ensure correct
repiacement of the motor (Figure 5-9).

5.3.5.2
l.

Remove the four screws attaching the motor to the mounting plate and remove the motor
through the top of the baseplate.

Motor Replacement
Insert the spindle motor through the top of the baseplate (Figure 5-7) and attach the motor
to the mounting plate with the previously removed hardware.

2. Push the spind1e motor mounting plate toward the spindle and slip the drive belt around the
pulleys.

5-16

3. Connect the spindle motor leads to TB4 (Figure 5-3) and to the spindle motor relay (Figure
5-Sa). Refer to the chassis wiring drawing for TB4 and the spindle motor relay connection
color code.
4. Check the read/write head alignment (Paragraph 5.4.5).
5.

Replace the top and bottom covers.

6. Slide the drive into the rack and connect the ac line cord.
7. Close the rear door.
Drive Belt Removal and Replacement

5.3.5.3
1.

Remove the disk cartridge from the drive.

2. Open the rear door of the rack and unplug the drive ac line cord.
3. Slide the drive out of the rack until it locks in the extended position.
4. Remove the bottom cover.
5.

Push the spindle motor mounting plate (Figure 5-Sa) toward the spindle to relieve belt
tension, and then slip the belt off the pulleys.

6. Clean the spindle and drive motor pulleys with a clean cloth moistened with 91 % isopropyl
alcohol.
7.

Install a new drive belt by pushing the spindle motor mounting plate toward the spindle and
slipping the drive belt around the pulleys. Do not stretch the belt!

Replace the bottom cover.

9. Slide the drive into the rack and connect the ac line cord.
10. Close the rear door.
5.3.6

Blower Motor

5.3.6.1
1.

Blower Removal (Figure 5-10)
Remove the disk cartridge from the drive.

2. Open the rear door of the rack and unplug the drive ac line cord.
3. Slide the drive out of the rack until it locks in the extended position.
4.

Remove the top and bottom covers.

Disconnect the blower leads from TB4 (Figure 5-3).

Remove the four blower mounting screws and carefully remove the blower and shroud from
the baseplate. Be careful not to damage the foam seal while removing the blower.

5-17

BLOWER LEADS

BLOWER MOTOR

MOUNTING SCREWS (4)

SHROUD

FOAM SEAL
6858-4

Figure 5-10 Blower Motor Removal

5-18

5.3.6.2

Blower Replacement

1. Secure the blower and shroud to the baseplate with the previously removed hardware.
2. Connect the blower leads to TB4.

3. Replace the top and bottom covers.
4. Slide the drive into the rack and connect the ac line cord.
5. Close the rear door.
5.3.7 Power Supply Removal
Close tolerances between the power supply package, the baseplate assembly, and the chassis may make
it necessary to remove the frontmost (+ 15 Vdc) regulator before removing the RK05 power supply
and assembly. The procedure is as follows:
1. Loosen the two captive screws that hold the frontmost regulator in place.

2. Remove that regulator.
3. There should now be enough room to remove the power supply.
5.3.8 Cartridge Cleaning
Professional cartridge cleaning is recommended wherever practicable. However, it may occasionally
become necessary for qualified DEC Field Service personnel to clean cartridges in a troubleshooting or
emergency ,maintenance situation. Application of this procedure by unqualified personnel will void
warranty on that cartridge and on any drive in which that cartridge is operated.
5.3.8.1

Cartridge Cleaning Procedure

1. Lay the cartridge bottom up on a clean, hard surface, such as a cleared desktop or table. In
this position the cartridge will tend to be somewhat unstable and may require support.
2.

Remove the screws that hold the cartridge top and bottom plastics together, using only
enough downward force on the screwdriver to hold it in the screwhead. Excessive force can
strip the threads of the plastic.

3. Pick up the disk by the hub, being careful not to hit the access door with the edge of the disk
when lifting it out of the cartridge.
CAUTION
Do not loosen the four screws in the hub holding the
clamping ring and filter ring to the disk; this would
permit the disk (and data) to move in relation to the
centering cone of the hub, which would cause the
data to become unrecoverable.
4.

Inspect the oxide surface of the disk for the following:
a.

"Comet tail" scratches - ding marks with tapering scratches caused by particles
embedded in the disk and then knocked out.

5-19

"Full circle" scratches - scratches caused by particles that remain stuck to the heads.
This condition requires that the heads be cleaned.

Single spot marks, dings, or scratches, with no associated circular scratches - usually
the result of dimples or bumps on the disk, or of the air inlet door being pushed into the
surface of the disk.

Black (burned) or dark brown streaks of oxide.

Fingerprints.
NOTE
A large number of small, shiny streaks all over a
well-used disk is evidence of normal head / disk
interference.

Inspect the hub for the following:
a.

Bent, nicked, or dirty sector slots in the sector ring.

Bent, nicked, or dirty mating cone or mating ring-plate.

6. Inspect the top plastic for the following:

Broken clear plastic seal on the access door.

Retaining button that retracts when the access door is opened.

Worn retaining button in center of the top.

Properly closing access door.

Signs of rubbing by the disk.

Spring load on the retaining button.

Inspect the bottom plastic for the following:
a.

Broken rivets on the air inlet door.

Signs of rubbing by the disk.

Fingerprints on the air inlet door.

Lay the disk on a spread-out Kimwipe on a desk or tabletop. Press down on the hub with
one hand to prevent the disk from tipping. With the other hand, wipe the surface of the disk
with a Texpad or Kimwipe soaked in 91% isopropyl alcohol. Wipe with small circular
motions around the circumference of the disk.
CAUTION
Use only 91% isopropyl alchohol for this purpose.
Water, trichloroethylene, and other solvents will
attack the epoxy binder of the oxide.

5-20

9. Wipe the disk dry with a dry Kimwipe before the alcohol evaporates. If the alcohol is permitted to evaporate by itself, residue spots on the oxide will result. If it is necessary to rub an
individual shiny spot or streak on the oxide, it should be done very gently; the surface of the
disk could be bent by pressing down too hard.
10. Turn the disk over, holding it by the hub only. Do not handle the disk by its edges; this
results in the deposit of finger oils that could be transferred to the oxide surface by further
WIPIng.
CAUTION
Dry lint may be blown off gently by mouth. Do not
spit on the disk. Do not use ordinary plant air, which
may contain an unacceptable level of water or oil;
canned air, however, is generally acceptable.
11. Wipe off the inside and outside of both the top and bottom plastics, taking care not to leave
any lint. Remove any portions of the clear plastic door seal that may break off during use of
the cartridge.
12.

Reassemble the cartridge. Locate the original threads in the top plastic screw holes by rotating the screw backward one or two revolutions before driving it. Use a minimum of downward force on the screwdriver to a void damaging the plastic threads and creating plastic
chips inside the cartridge.

5.3.8.2 Adverse Disk Conditions - The disk will probably cause damage to the heads if used in the
following conditions:
1. The center retaining button shows signs of rubbing on the hub cone of the disk. This creates
particles inside the cartridge during operation and allows the disk to rattle around inside the
cartridge during handling.
2. The air inlet door is loose, or has broken rivets.
3. There are signs of disk rubbing on the insides of the cartridge.
4. The disk has nonremovable scratches or dings which stick up above the smooth oxide
surface.
5.

The disk causes continual tinging sounds after the usual single short ting that accompanies
loading.

6. The disk continually deposits oxide on the heads.
CAUTION
If known good disks deposit oxide on the heads, the
heads themselves may be at fault.
7.

The disk has a hard and locatable error.

Cartridges displaying the above conditions can probably be used once more, if necessary, to recover
critical data, but should be refurbished immediately thereafter, lest the heads crash and get destroyed.
Disks have been known to transfer data reliably despite having aluminum exposed through the oxide;
conversely, disks have been known to crash heads despite having no visible scratches. The ultimate test
of an acceptable disk must be whether it transfers data reliably while leaving the heads clean.
5-21

5.4 ALIGNMENT, CHECKS, AND ADJUSTMENTS
5.4.1

Alignment Cartridges

5.4.1.1 RK05K-AC Alignment Cartridge - This Digital Equipment Corporation alignment cartridge
is preferred for RK05 and RK05-J alignment procedures. It provides three tracks (principal track 105,
plus spare tracks 85 and 125) of constant frequency data and alternate sectors recorded at displacements of +0.0025 and -0.0025 inches, respectively, from the ideal track locations. Figure 5-11
shows how to read the vernier when locating the desired track.
To determine the vernier scale reading:
1.

Take the whole number value of the nearest positioner track scale marking to the right of the
vernier scale triangle (i.).

Take the value of the vernier scale marking that aligns perfectly with a positioner track scale
marking.

Add these two values to find the vernier reading.

In Figure 5-11, the nearest positioner track scale marking to the right of the triangle is 100; the vernier
scale value that aligns perfectly with a positioner track scale marking is 5. Therefore, the vernier is set
to Track 105 (100 + 5).
When a head is aligned to specifications, the readback signal shows equal amplitudes for both sectors
(shown when the oscilloscope displays only two sectors, and triggered by the SECTOR signal). The
degree of amplitude inequality in alternating sectors indicates the departure from exact alignment.
Sector timing data is included on all three tracks to indicate head gap location relative to sector pulse
detection. This data is represented by a single pulse (70 JJ,S nominal) triggered by the INDEX pulse 10
JJ,S prior to the onset of head alignment data.

[~ I ; I : s::~ ~
'"

PERFECTLY

ALIGNED

" " ' - - VERN !ER SCALE

Figure 5-11

How to Read a Vernier

5-22

The RK05K-AC alignment cartridge also indicates the degree of runout on the spindle. When the
oscilloscope is triggered on INDEX and a complete revolution of the disk is displayed, the head may
appear to be aligned at some sector locations and misaligned at others. This condition indicates the
degree of wobble of the spindle. Figure 5-12 shows a display with negligible runout; Figure 5-13 shows
a spindle with considerable runout. The amount of wobble can be determined by the amplitude differences occurring in any adjacent pair of sector boundaries using the same equations used for head
alignment.
NOTE
If the condition shown in Figure 5-13 exists, ensure
that the mating of spindle and disk is clean. Improper
mating can cause such runout.
Specifications for the RK05K-AC alignment cartridge when used with the RK05 and RK05-J are as
follows:
Alignment and Sector Timing Tracks - primary track - 105; backup tracks - 85, 125, (use only if
track 105 is unusable)
Recorded Frequency - nominal 720 kHz
Number of Sectors - 12
Alignment Accuracy, track 105 - ±200 micro inches
Sector Timing - single pulse 70 ± 12 p,s following INDEX pulse.
The RK05-AC alignment cartridge can be adapted for use by the RK05-F Disk Drive. To select the
odd drive, ground A08K2 or A08M2. Only RK05-J track 105 may be used as an alignment track for
the RK05-F. (This is because the 0.005053-inch center-to-center spacing of the RK05-F tracks will not
divide evenly into the 0.010-inch center-to-center spacing of the RK05 and RK05-J tracks.)
RK05-J Tracks
85
105
125

RK05-F Tracks
Odd drive

5.4.1.2 2315 CE Test Cartridge Shim Installation - (To be used only when an RK05-AC alignment
cartridge is not available.) Before a 2315 test cartridge can be used for any RK05 alignment procedure,
a 0.D05-inch shim must be installed in the disk hub. Because the 2315 cartridge is recorded at low
density and the RK05 uses a high-density cartridge, this shim is required to accentuate the wobble of
the low-density cartridge and allow it to be used for high-density alignments. To install the shim
properly, trim a piece of 0.OO5-inch shim stock, as indicated in Figure 5-14, and attach it to the disk
hub as follows:
1.

Locate sector 00 by holding the cartridge upside down and 0 bserving the sector slots in the
metal lip of the disk hub. Rotate the disk clockwise inside the plastic case until two slots
close together are located (sector 11 and index slots). Continue to rotate the disk clockwise,
stopping at the next slot (sector 00).

Position the shim 180 degrees from the sector 00 slot. Ensure that the narrow portion of the
shim is in the spindle cavity and that the shim does not reach the bottom of the cavity.

Tape the shim in position.
5-23

Figure 5-12

Negligible Runout

Figure 5-13

Considerable Runout

5-24

\E~TOR 0
\LOT

INDEX
SLOT

' - - - - - - VI EW A - - - - - - '

1I-----.rj+-1/16

31 8 II

SHIM~I

THICKNESS =.005"

CP-0513

Figure 5-14 CE Test Cartridge Shim Installation

5.4.2 Servo System Timing Checks and Adjustments
The servo system timing adjustments are precisely set at the factory and should not be routinely adjusted or fine tuned as part of any PM procedure. If a positioner malfunction is suspected, all waveforms
related to each phase of servo operation should be examined; based on these, the possible trouble
should be diagnosed before any servo adjustments are attempted. Because some of the servo check
tolerances differ from the adjustment tolerances, reference should be made to the check tolerances in
Table 5-3 before adjustments are attempted.

NOTE
Settings within the tolerances listed in Table 5-3
should NOT be adjusted.

5-25

Table 5-3 Servo System Checks

-Checks

Drive Configuration

I Test Point I

Sine Amplitude/Offset

4 cyl osc seek

Velocity Offset

Tolerance

Reference

A05MI

10 ± 1 V p-p, ground
symmetrical within
±10%

Fig. 5-15

4 cy1 osc seek

A05Ml

ground symmetrical
within ± 10%

Fig. 5-15

Cosine Amplitude

4 cy I osc seek

A05S1

10 ± 1 V p-p, ground
symmetrical within
±10%

Fig. 5-16

Velocity Amplitude
(RK05/RK05-J)
(RK05-F)

2 cy I osc seek

A05M1

center pulse duration

Fig. 5-17

= 3.2 ± 0.05 ms
= 2.3 ± 0.1 ms

Acceleration
(RK05/RK05-J)
(RK05-F)
Full Stroke Profile
(RK05/RK05-J)

64 cy I osc seek
128 cyl osc seek

A05H1

202 cyl osc seek

A05HI

i
r

(logical disk)
(RK05-F)
Full Stroke Position
(logical disk)

Outer Limit

14 ms ± 1 ms rise time Fig. 5-18
13 ms ± 1 ms rise time
<90 ms waveform
Fig. 5-19
duration with plateau
at trailing edge.
< 70 ms waveform

202 cy I osc seek

A05M1

equal beginning and
end amplitudes
within 5%.
< I V overshoot

Fig. 5-20

rep RTZ

A05J1

3 to 3.5 V amplitude
<0.3 V plateau

Fig. 5-21

F or most maifunction cases, the positioner system will operate enough to allow dynamic measurements. However, if the positioner either does not operate or operates very erratically, the static checks
and adjustments described in Paragraph 5.4.2.2 should be performed.
If servo system parts are field-installed, settings must be readjusted according to Table 5-3.
5.4.2.1 Dynamic Off-Line Checks and Adjustments - If on-line diagnostics or an RK05 Exerciser are
not available to exercise the positioner, the RK05 should be disconnected from the interface bus and
operated off-line.
In this mode, SECTOR pulses are jumpered to simulate STROBE pulses, and a SECTOR ADDRESS
line is jumpered to provide changing inputs to selected CYLINDER ADDRESS lines. These jumper
installations permit oscillating seeks between cylinder 00 and any selected cylinder to be performed.
5-26

The procedure for operating the drive off-line is as follows:
1.

Unplug the drive ac line cord to remove power.

Install an M930 terminator card in position 7 or 8 of the electronic module.

Set the address select switch on the M7680/M7700 card (position 2) to the first switch
position.

Select the drive by connecting ajumpei from A08Tl (ground) to A08J2 (switch position 1).

Reconnect the ac line cord to apply power to the drive and cycle the drive up to operating
status.

Perform an off-line oscillating seek with the jumpers as follows:

It is also possible to perform the following adjustments using the RK05-TA Exerciser or simple
test programs. For additional information, refer to the RK05 Exerciser Maintenance Manual,
(DEC-OO-HZRKA-A-D).
a.

Connect a jumper from B08H I (STROBE) to B08N2 (BUS SECTOR PULSE).

Determine the seek length by connecting A08P2 (SECTOR ADDRESS) to the desired
points indicated in the following table.
Seek Length

Jumper Connections

A08Dl

A08Ll

A08EI

100

A08EI, A08Jl, A08Ll

105

A08El, A08JI, A08Cl, A08Kl

128

A08Hl

202

A08HI, A08El, A08CI, A08Dl

Restore (R TZ)*

A08M I (RESTORE)to A07T 1
(or any available ground)
B08H 1 (STROBE) to
B08MI (INDEX)

*Connect only the points listed in the table.

5-27

Unless otherwise indicated, set the oscilloscope controls (Tektronix 453 or equivalent) as
follows:
vertical
mode
sensitivity
trigger
coupling

=
=
=
=

channell
2 V/div
channell
dc

sweep
A sweep time
trigger

=
=

10 ms/div
normal

trigger
source
coupling
slope

=
=
=

externals·
ac

*Connect the scope external trigger input
to B05J2 (FWD H).

To avoid excessive scope control changes and to keep the probe test point changes to a
minimum, perform the following checks and adjustments in the listed sequence.
Sine Amplitude (SA) and Offset (SO)
a.

Perform a 4-cylinder oscillating seek (Step 6).

Observe A05M I (SIN POSITION) for a scope display similar to that shown in Figure
5-15a. The waveform amplitude must be 10 ± I V peak-to-peak and symmetrical about
ground.

If necessary, adjust SA (Table 5-4) for the correct amplitude and SO for the ground
symmetry.

Velocity Offset (VO)
a.

Perform a 4-cylinder oscillating seek (Step 6).

Observe that the voltage minimums at A05M I (SIN POSITION) are symmetrical
about ground (Figures 5-15a and 5-15b). A small amount of ripple at the minimum
voltage levels is normal. To estimate the degree of symmetry, use the average value of
the ripple as the voltage minimum.

If necessary, adjust VO (Table 5-4) for the required symmetry.

Cosine Amplitude (CA) and Offset (CO)
a.

Perform a 4-cylinder oscillating seek (Step 6).

Observe A05S1 (COS POSITION) for a scope display as shown in Figure 5-16. The
waveform amplitude must be 10 ± 1 V peak-to-peak, and symmetrical about ground.

If necessary. adjust CA (Table 5-4) for the correct amplitude and CO for the ground
symmetry.

5-28

SIGNAL RETURNS
TO GROUND
LEVEL

OV---

A05M1

SWEEP

10 ms/div

VERT SENS

2V/div

(a) Correct Waveform (Symmetrical Signal)

SIGNAL DOES NOT
RETURN TO
GROUND LEVEL

M0330

(b) Incorrect Waveform (Signal not Symmetrical about Ground)

Figure 5-15

Sine Amplitude/Offset and Velocity Offset Waveform

5-29

Table 5-4

Servo System Adjustments

Potentiometer*

Function

CA (Cosine Amplitude)

Sets amplitude of COS POSITION signal.

CO (Cosine Offset)

Adjusts COS POSITION symmetry about ground.

SA (Sine Amplitude)

Sets amplitude of SIN POSITION signal.

SO (Sine Offset)

Adjusts SIN POSITION symmetry about ground.

LSA (Limit Signal Amplitude)

Simultaneously adjusts amplitude of both Limit signals before
digitizing.

LSO (Limit Signal Offset)

Sets zero level of Limit signal with positioner in normal
recording area of disk.

VA (Velocity Adjustment)

Calibrates velocity generator.

VO (Ve1ocity Offset)

Adjusts velocity generator output at zero velocity. (Provides
offset control to position loop.)

CURRENT (on H604)

Sets maximum positioner current (determines acceleration).

*Potentiometers are located on the G938/G938YA card (position 5) of the logic assembly; access is obtained by removing the
prefilter. They are listed in the table according to their physical orh:ntatiun; eA is the topmost potentiometer as viewed from
the rear of the drive with the prefilter removed.

OV
PIN
SWEEP
VERT SENS

Figure 5-16

Cosine Amplitude/Offset Waveform

5-30

A05S1
10ms/div
2V/div

Velocity Amplitude (VA)
a.

Perform a 2-cylinder oscillating seek (Step 6).

Set the scope sweep time to 1 ms/div.

Observe A05M 1 for a scope display as illustrated in Figure 5-17. The duration of the
center cycle must equal 3.2 ± 0.05 ms (2.3 ± 0.1 ms for the RK05-F).

If necessary, adjust VA (Table 5-4) for the correct time.

fN
t ;;:; 3.2 ms for RK05/RK05J
t .-:::: 2,3 ms for RK05F

Figure 5-17

A05M1

SWEEP

1 rns/div

VERT SENS

2V/dlv

Velocity Amplitude Waveform

Acceleration (Positioner Current)
a.

Perform a 64-cylinder oscllating seek (Step 6) (128-cylinder for RK05-F).

Set the scope sweep time to 5 ms/div and the vertical sensitivity to 0.5 V /div.

Observe A05H 1 (VELOCITY) for a velocity profile as shown in Figure 5-18.

If necessary, adjust R 15 (on H604) for a rise time of 14 ms ± 1 ms (13 ± 1 ms for
'0
Tl" r,,_p\
.'-..I.'1Irrrr...v....,- ... , .

5-31

t :::: 14 ms for RK05/RK05J
t "'" 13 inS for RK05f

Figure 5-18

A05H1

SWEEP

5 msfdiv

VERTSENS

O.5V/div

Acceleration Waveform

Full Stroke Profile
a.

Peiform a 202-cylinder oscillating seek (Step 6).

Set the scope sweep time to 10 ms/div and the vertical sensitivity to 0.5 V/div.

Observe A05Hl (VELOCITY) for a scope display as illustrated in Figure 5-19. The 0 V
level of the profile must be reached in less than 90 ms from the start of the seek (70 ms
for RK05-F).
In addition, there must be a definite plateau (constant voltage level) at the end of the
seek. If this is not the case, recheck the VA and the Acceleration (Positioner Current).
Adjust the appropriate potentiometer (Table 5-4) as required to obtain the correct
waveform.

Full Stroke Position Waveform
a.

Maintain the same configuration as for the Full Stroke Profile.

Set the scope vertical sensitivity to 2 V/div and observe A05Ml (SIN POSITION) for a
scope display as illustrated in Figure 5-20. The waveform amplitudes at the start and
end of the seek must be equal within 5%, and the overshoot at the end of the seek must
not exceed IV. If overshoot is excessive, recheck the VA and the Acceleration (Positioner Current).

5-32

t ;:::: JOms for H KGBF

Af)5H1

10 ms/dlv
f). SV/d!v

Figure 5-19

Full Stroke Waveform

OVERSHOOT < 1V

PIN
SWEEP
VERTSENS

Figure 5-20 Full Stroke Position Waveform

5-33

A05M1
10 ms/div
2V/div

Outer Limit (Dynamic Test)
a.

Perform a repetitive restore operation (Step 6).

Trigger the scope from B05K2 (REV H).

Set the scope vertical sensitivity to 1 V /div and observe A05Jl (LIMIT) for a scope
display as illustrated in Figure 5-21. The waveform peak amplitude must be 3 to 3.5 V
with a minimum level of 0 V. In addition, the voltage plateau immediately following
the trailing edge must not exceed 0.3 V. If not, perform the static limit adjustment
procedure (Paragraph 5.4.2.2).

Disconnect the B08H 1 (STROBE) jumper to halt the repetitive restore.

Check the INNER LIMIT signal by physically moving the positioner to the inner limit
(toward the spindle). If the INNER LIMIT signal is operative, a restore operation will
be initiated. If this is not the case, perform the static limit adjustment procedure (Paragraph 5.4.2.2).

PLATEAU

<O.3V

PIN
SWEEP
VERTSENS

Figure 5-21

A05Jl
1 ms/div
1V/div

Outer Limit Waveform

5.4.2.2 Static Tests and Adjustments - The following procedure should be performed when the
positioner or a major servo system component has been replaced. This procedure should also be
followed as a diagnotic aid when the positioner system is inoperative or unstable in operation.
To make the required adjustments, remove the disk cartridge from the drive and physically move the
positioner carriage back and forth while observing the selected signal. Use the automatic scope sweep
and do not attempt to sync the sweep to the observed signal. With a little practice, the most convenient
sweep speed setting and the type of positioner motion required will quickly be discovered.

5-34

To make static adjustments, the following procedure should be followed:
1. Do not install a disk cartridge in the drive.
2. Place a finger on the positioner carriage assembly and then place switch S 1 (Figure 4-17) in
the down or OFF position. (This precaution prevents any possible carriage motion caused
by transient switch noise.)
3. Make the following checks and adjustments.
Sine Amplitude (SA) and Offset (SO)
a.

Set the scope vertical sensitivity to 2 V / div and adjust the ground reference to the
center of the scope screen.

Observe A05M 1 (SIN POSITION) while manually moving the positioner back and
forth. Adjust SA (Table 5-4) for a 10 V ± 1 V peak-to-peak signal amplitude.

Adjust SO until the signal is symmetrical about ground.

Cosine Amplitude (CA) and Offset (CO)
Observe A05S 1 and adjust CA and CO (Table 5-4) in the same manner as that used in the
Sine Amplitude and Offset pr.ocedure, above.
Limit Signal Amplitude (LSA) and Offset (LSO)
a.

Set the scope vertical sensitivity to 1 V / div and adjust the ground reference to the
center of the scope screen.

Observe A05J 1 with the positioner stationary at approximately the center of travel.
Adjust LSO (Table 5-4) for a ground signal at the center of the scope screen.

Move the positioner to the inner limit and observe the voltage change on the scope.
Similarly, move the positioner to the outer limit and observe the voltage change.

Adjust LSA until the smaller voltage level obtained in Step c, above, is 3.0 V.

Return the positioner to the center of travel and readjust LSO for 0 V.

Repeat Step c, above; if necessary, readjust the smaller voltage level to 3.0 V.

5.4.3 Read/Write Data Separator (G180 Card) Adjustment
Adjustment of the data separator is not part of normal maintenance and is therefore not recommended
unless a G 180 component that affects the data separator section has been replaced. If this occurs, the
width of the data window should be set as follows:
CAUTION
R 13 is the wiite CUiient adjustment potentiometer
and cannot be adjusted in the field.
1. Install a prerecorded cartridge in the drive.

5-35

Place the drive in the run mode and manually position the heads at any recorded cylinder
past track zero, An all-zero recording is preferable; however, any recorded pattern is
sufficient.
NOTE
To position the heads manually, allow them to load
under servo control; then place a finger on the carriage while opening the switch (S 1) to preclude the
possibility of carriage motion caused by the transient
switch noise.

Set the oscilloscope controls as follows:
vertical
mode
sensitivity
trigger
coupling

=
=
=
=

channell
1 V /div
channell
dc

sweep
A sweep time
trigger

=
=

100 ns/div
normal

trigger
source
coupling
scope

=
=
=

internal
ac

Connect the channell scope probe to TPI of the G180 card (card position 1). It should be
possible to obtain solid scope synchronization at the sweep start. (Disregard the unsynchronized pulses that follow.)

Adjust R55 fully counterclockwise and R54 fully clockwise.

Adjust R54 counterclockwise to obtain a 500 ± 40 ns pulse width as measured from the start
of the rise to the start of the fall.

Readjust R55 clockwise until the pulse width decreases to 440 ± 10 ns as measured from the
start of the rise to the start of the fall.

5.4.4 Read/Write Head Check and Alignment
The foHowing procedure describes the complete read/write head alignment. Before attempting this
alignment procedure, ensure that the drive operates correctly and that the heads have not been contaminated by exposure to a defective cartridge. If new heads have been installed, it is recommended
that this alignment procedure be performed off-line using backboard jumpers to move the positioner
to the alignment cylinder. Off-line alignment is strongly recommended because of the ease of returning
to the alignment cylinder whenever the positioner has been physically moved. However, simple
maintenance routines or an RK05 Exerciser may also be used to move the positioner.
5.4.4.1 RK05K-AC Alignment Cartridge - The appropriate on-line diagnostics may be used for head
alignment; however, do not adjust a head that has less than a 15% error (Figure 5-22).

5-36

Extreme misalignment. Head close to
CYL 104. (Further misalignment only
reduces amplitude of signal on right
side of screen.)

Head considerably misaligned. Smaller
left amplitude indicates head position
less than CYL 105.
error =-72%

BRIGHT LINE
SHOU LO APPEAR
HERE

Head slightly misaligned. Smaller left
amplitude indicates head position less
than CYL 105.
error =-15%

BRIGHT LINE
SHOU LO APPEAR
HERE

Figure 5-22

RK05K-AC Head Alignment Waveforms (Sheet 1 of 3)

5-37

Head correctly aligned at CYL 105.
Amplitudes are equal.

BRIGHT LINE
SHOU LD APPEAR
HERE

Head slightly misaligned. Larger left
amplitude indicates head position
more than CYL 105.
error = +15%

BRIGHT LINE
SHOULD APPEAR
HERE

Head considerably misaligned. Larger
left amplitude indicates head position
more than CYL 105.
error =+72%

BRIGHT LINE
SHOULD APPEAR
HERE

Figure 5=22

RKOSK-AC Head Alignment \Vavcfoims (Sheet 2 of 3)
5-38

BRIGHT LINE
SHOULD APPEAR
HERE

Extreme misalignment. Head close to
CYL 106. (Further misalignment only
reduces amplitude of signal on left side
of screen.)

To calculate % of error, use the following formula:

% error =

Xl Xl

+ X2

X 100

Xl and X2 = amplitudes. The resultant sign denotes
the direction of error; a negative (-) sign indicates
that the head is back too far.

Figure 5-22

RK05K-AC Head Alignment Waveforms (Sheet 3 of 3)

5-39

aligr '::'If check the heads, proceed as follows:

Unplug the drive ac line cord to remove power.

Disconnect the drive interface cable card from the logic assembly and install in its place an
M930 terminator card.

Reconnect the ac line cord to bring the drive up to operating status.

Install an alignment cartridge on the spindle and operate the drive in the run mode for at
least 30 minutes. This must be done to allow the alignment cartridge and the drive components to achieve thermal stabilization.

Using the WT PROT switch, place the drive in the write protect condition.

Set the oscilloscope controls as follows:
vertical
mode
sensitivity
coupling

=
=
=

ADD (invert CHAN 2)
20mV/div
de

sweep
A sweep time
trigger

=
=

500 Jls/div
normal

trigger
source
coupling

=
=

externai*
ac

*Important: Use a 1:1 probe to connect the scope external trigger input to A02S2 (SECTOR).
7.

Connect the channell probe to TP3 and the channel 2 probe to TP4 of the GI80 card. (Use
10: 1) probes.)

Ensure that the positioner track scale indicates cylinder 00. If it does not, loosen and readjust the scale to read 00, ensuring proper scale readout over the entire length of the head.
This is done as follows:
a.

Load the heads.

Check whether the scale is set at zero; if not, loosen the scale retaining screws (Figure 523).

Adjust the fixed scale horizontally to read zero. Ensure that the calibrated edges of the
fixed scale and the vernier scale are parallel and close together without touching. Tighten the scale retaining screws.

Push S 1 (Figure 4-17) down, and move the vernier scale horizontally through its entire
range to ensure that the calibrated edges of the two scales do not touch at any point.

5-40

TRACK POSITION
SCALE

SCALE RETAINING
SCREWS

VERNIER
SCALE

LOWER HEAD
ADJUSTMENT
SCREW

UPPER HEAD
ADJUSTMENT
SCREW

UPPER HEAD
CLAMP SCREW

LOWER HEAD
CLAMP SCREW

HEAD SUPPORT
ARM

6858-5

(a)

HEAD ADJUSTMENT
SCREWS

LOWER HEAD
CLAMP SCREW

UPPER HEAD
CLAMP SCREW

(b)

Figure 5-23

Read/Write Head Adjustments

5-41

For the RK05 or RK05-J drives, select cylinder 105 as follows:
NOTE
It is also possible to perform the following adjustments using the RK05 Exerciser or simple maintenance routines. For additional information, refer to
the RK05 Exerciser Maintenance Manual.
a.

Connect backboard jumpers from A07Tl, A07C2, B07Tl, or any available ground pins
to the following points:
.
A08El

CYL ADD 6(64)

A08Jl

CYL ADD 5(32)

A08CI

CYL ADD 3(8)

A08KI

CYL ADD 0(1)
105

A04Vl
b.

SEL RDY L

Connect ajumper from B08Hl (STROBE) to B08N2 (SECTOR PULSE). The positioner should move tq cylinder 105. Confirm this by observing the track scale indicator.

For the RK05-F drive, select cylinder 5, odd drive, as follows:

Connect backboard jumpers from A07Tl, A07C2, B07Tl, or any available ground pins
to the following points:
A08K2 ODD DRIVE
A08M2
A08L I

CYL ADD 2(4)

A08Kl

CYL ADD 0(1)

5
A04VI
b.
10.

SEL RDY L

Connect ajumper from B08Hl (STROBE) to B08N2 (SECTOR PULSE). The positioner should move to cylinder 5. Confirm this by observing the track scale indicator.

Monitor the scope display for one of the waveforms illustrated in Figure 5-22.
NOTE
A bright horizontal line should appear at the beginning (left) of the displayed waveform, as shown in
Figures 5-22b through 5-22g. If the line does not
appear, adjust the scope level control until it does.
This bright line indicates proper positioning of the
sectors; odd sectors (Xl) on the left, even sectors
(X2) on the right.
5-42

If none of the illustrated waveforms appear, the head is so badly misaligned that manual
manipulation of the positioner is required. If manual manipulation is required, perform the
steps that follow; if not, proceed to Step 11.

Place switch S 1 (Figure 4-17) in the down or OFF position, keeping a finger on the
carriage while manipulating the switch to dampen any positioner transients.

Slowly move the positioner by hand until the alignment pattern occurs. Cylinders 85
and 12S have identical patterns, so be sure that the displayed pattern is for cylinder lOS
(S for the RK05=F). Do not use undue force on the positioner when manually changing
track positions.

Observe the track scale and note the cylinder indication when the correct waveform
(Figure S-22d) is obtained. If the scale indicates less than 105 (S for the RKOS-F), the
head is too far forward in the carriage. Conversely, if the scale indicates more than lOS
(S for the RK05-F), the head is too far back in the carriage.

Loosen the clamp and adjustment screws (Figure 5-22) and move the head in the
appropriate direction until the correct waveform (Figure 5-22d) is obtained and the
scale indication is slightly greater than 105 (5 for the RK05-F Disk Drive).
Tightening the clamp screw firmly will cause the head to move foward slightly, bringing
the scale indication to lOS (S for the RK05-F).

Lightly tighten the clamp screw and turn on the positioner power (S 1 up).

After turning off positioner power, move the positioner fully forward. Turn on positioner power (S 1 up) to initiate a restore (R TZ) operation. The positioner will automatically return to cylinder lOS following the RTZ (cylinder 5 for RKOS-F).

11. If one of the illustrated waveforms is present, note in which direction the head must be
moved to obtain the correct indication (Figure 5-22d). If it must be moved backward, loosen
the head clamp and adjustment screws and gently push the head all the way back into the
carriage; if it must be moved forward, loosen only the clamp screw, and then turn the
adjustment screw until the correct waveform is obtained.
The adjustment screw is a vernier that only moves the head forward; it should not be left
torqued down after this adjustment.
NOTE
If the positioner is moved from cylinder 105 (or 5)
during the adjustment procedure, turn off positioner
power (Sl down) and manually move the positioner
fully forward. Then turn on positioner power (Sl up)
to initiate a restore (RTZ) operation. The positioner
will automatically return to cylinder 105 following
the RTZ (cylinder 5 for RK05-F).

13. Using the appropriate torque wrench (Paragraph S.3.3.1), tighten the head clamp screw until
the wrench begins to ratchet. If a torque wrench is not available, use the appropriate Allen
wrench to tighten the head clamp screw snugly; do not overtighten.
14. Recheck to ensure that the clamping action did not disturb the head adjustment.
S-43

5.4.4.2 2315 CE Pack - The appropriate on-line diagnostics may be used for head alignment; however, do not adjust a head that has less than a 15% error (Figure 5-24),
To align or check the heads proceed as follows:
NOTE
Do NOT use this procedure with the DEC RK05KAC Alignment Cartridge; use the procedure from
Paragraph 5.4.4.1.
1. Unplug the drive ac line cord to remove power.
2.

Disconnect the drive interface cable card from the logic assembly and install an M930 terminator card in its place.

3. Reconnect the ac line cord to apply power to the drive and cycle the drive up to operating
status.
4.

Install a 2315 CE test cartridge on the spindle and operate the drive in the run mode for at
least 30 minutes. This must be done to allow the CE cartridge and the drive components to
achieve thermal stabilization.

Using the WT PROT switch, place the drive in the write protect condition.

6. Set the oscilloscope controls as follows:
.,,, .. 4-;0 ... 1
'IL-.... IL-A.

mode
sensitivity
coupling

=
=
=

ADD (invert CHAN 2)
20 mV /div
dc

sweep
A sweep time
trigger

=
=

10 ms/div
normal

external*
ac

trigger
source
coupling

*Important: Use a 1:1 probe to connect the scope external trigger input to A02R2 (INDEX).
7. Connect the channel 1 probe to TP3 and the channel 2 probe to TP4 of the G 180 card. (Use
10:1 probe.)
8.

Ensure that the positioner track scale indicates cylinder 00. If it does not, loosen and
readjust the scale to read 00, ensuring proper scale readout over the entire length of the
head. This is done as follows:
a.

Load the heads.

Check whether the scale is set at zero; if not, loosen the scale retaining screws (Figure 523).

5-44

Extreme misalignment. Head close to
CYL 104. (Further misalignment only
reduces amplitude of peaks.)

Head considerably misalgined. Smaller
left null indicates head position less
than CYL 105.
error =-60%

Head slightly misaligned. Smaller: left
null indicates head position less than
CYL 105.
error =-33%

Figure 5-24

2315 CE Pack Head Alignment Waveforms (Sheet 1 of 3)
5-45

Head correctly aligned at CYL 105.
Null amplitudes are equal.

Head slightly misaligned. Larger left
null indicates head position more than
CYL 105.
error =+26%

Head considerably misaligned. Larger
left null indicates head position more
than CYL 105.
error = +71 %

5-46

Extreme misalignment. Head close to
CYL 106. (Further misalignment only
reduces amplitude of peak.)

To calculate % of error, use the following formula:

% error =

Xl Xl

+ X2

X 100

Xl and X2 = null amplitudes. The resultant sign
denotes the direction of error; a negative (-)
sign indicates that the head is back too far.

Figure 5-24

2315 CE Pack Head Alignment Waveforms (Sheet 3 of 3)
5-47

Adjust the fixed scale horizontally to read zero. Ensure that the calibrated edges of the
fixed scale and the vernier scale are parallel and close together, without touching.
Tighten the scale retaining screws.

Push S 1 (Figure 4-17) down and move the vernier scale horizontally through its entire
range to ensure that the calibrated edges of the two scales do not touch at any point.

For RK05 or RK05-J drives with 2315 CE Pack, select cylinder 105 as follows:
NOTE
It is also possible to perform the following adjustments using the RK05 Exerciser or simple maintenance routines. For additional information, refer to
the RK05 Exerciser Maintenance Manual.
a.

Connect backboard jumpers from A07Tl, A07C2, B07Tl, or any available ground pins
to the following points:
AOSEI

CYL ADD 6(64)

A08Jl

CYL ADD 5(32)

AOSCI

CYL ADD 3(S)

AOSKI

CYL ADD 0(1)

105
A04Vl
b.

SEL RDY L

Connect a jumper from BOSH 1 (STROBE) to B08N2 (SECTOR PULSE). The positioner should move to cylinder 105. Confirm this by observing the track scale indicator.

For RK05-F drive with 2315 CE Pack, select cylinder 5 as follows:
a.

Connect backboard jumpers from A07Tl, A07C2, B07Tl, or any available ground pins
to the following points:
AOSK2 ODD DRIVE
AOSM2
AOSL 1 CYL ADD 2(4)
AOSKI

CYL ADD 0(1)

5
A04Vl
b.

SEL RDY L

Connect a jumper from B08Hl (STROBE) to B08N2 (SECTOR PULSE). The positioner should move to cylinder 5. Confirm this by observing the track scale indicator.

5-4S

10. Monitor the scope display for one of the waveforms illustrated in Figure 5-24.
NOTE
A bright horizontal line should appear at the beginning (left) of the displayed waveform, as shown in
Figures 5-24b through 5-24g. If the line does not
appear, adjust the scope level control until it does.
This bright line indicates proper positioning of the
sectors; odd sectors (Xl) on the left, even sectors
(X2) on the right.
If none of the illustrated waveforms appear, the head is so badly misaligned that manual
manipUlation of the positioner is required. If manual manipulation is required, perform the
steps that follow; if not, proceed to Step 11.
a.

Place switch S 1 (Figure 4-17) in the down or 0 FF position, keeping a finger on the
carriage while manipulating the switch to dampen any positioner transients.

Slowly move the positioner by hand until the alignment pattern occurs. Cylinders 85
and 125 have identical patterns, so be sure that the displayed pattern is for cylinder 105
(5 for the RK05-F). Do not use undue force on the positioner when manually changing
track positions.

Observe the track scale and note the cylinder indication when the correct waveform
(Figure 5-24d) is obtained. If the scale indicates less than 105 (5 for the RK05-F), the
head is too far forward in the carriage. Conversely, if the scale indicates more than 105
(5 for the RK05-F), the head is too far back in the carriage.

Loosen the clamp and adjustment screws (Figure 5-23) and move the head in the
appropriate direction until the correct waveform (Figures 5-24d) is obtained and the
scale indication is slightly greater than 105 (5 for the RK05-F Disk Drive). Tightening
the clamp screw firmly will cause the head to move forward slightly, bringing the scale
indication to 105 (5 for the RK05-F).

Lightly tighten the clamp screw and turn on the positioner power (SI up).

11. If one of the illustrated waveforms is present, note in which direction the head must be
moved to obtain the correct indication (Figure 5-24d). If it must be moved backward, loosen
the head clamp and adjustment screws and gently push the head all the way back into the
carriage; if it must be moved forward, loosen only the clamp screw, and then turn the
adjustment screw until the correct waveform is 0 btained.

5-49

The adjustment screw is a vernier that only moves the head forward; it should not be left
torqued down after this adjustment.
NOTE
If the positioner is moved from cylinder 105 (or 5)
during the adjustment procedure, turn off positioner
power (SI down) and manually move the positioner
fully forward. Then turn on positioner power (SI up)
to initiate a restore (RTZ) operation. The positioner
will automatically return to cylinder 105 following
the RTZ (cylinder 5 for RK05-F).
12. Ground B08M2 to select the upper head and repeat the preceding steps.
13. Using the appropriate torque wrench (Paragraph 5.3.3.1), tighten the head clamp screw until
the wrench begins to ratchet. If a torque wrench is not available, use the appropriate Allen
wrench to tighten the head clamp screw snugly; do not overtighten.
14. Recheck to ensure that the clamping action did not disturb the head adjustment.
5.4.5

Index/Sector Timing Adjustment

5.4.5.1

RK05K-AC Alignment Cartridge
1. Unplug the drive ac line cord to remove power.

Disconnect the drive interface cable card from the electronic module and install an M930
terminator card in its place.

3. Reconnect the ac line cord to bring the drive up to operating status.
4. Install an RK05K-AC alignment cartridge on the spindle, ensuring that the mating surfaces
are clean; operate the drive in the run mode for at least 30 minutes. This must be done to
allow the alignment cartridge and the drive components to achieve thermal stabilization.
5. Using the WR PROT switch, place the drive in the write protect condition.

6. Set the oscilloscope controls as follows:
vertical
mode
sensitivity
coupling

=
=
=

sweep
A sweep time =
=
trigger
trigger
source
coupling
slope

=
=
=

ADD (invert CHAN 2)
0.2 V/div
dc
5 ms/div
normal
external·
ac

*Important: Use a 1:1 probe to connect the scope external trigger input to A02R2 (INDEX).

5-50

7. Connect the channel I probe to TP3 and the channel 2 probe to TP4 of the G 180 card. (Use
10: I probes.)
8.

Ensure that the positioner track scale indicates cylinder 00 (Paragraph 5.4.4.1, Step 8).

For the RK05 or RK05-J drives, selct cylinder 105 as follows:
NOTE
It is also possible to perform the following adjustments using the RK05 Exerciser or simple test
programs.
a.

Connect backboard jumpers from A07Tl, A07C2, or any available ground pins to the
following points:
A08EI

CYL ADD 6(64)

A08JI

CYL ADD 5(32)

A08CI

CYL ADD 3(8)

A08KI

CYL ADD 0(1)
105

A04VI
b.

SEL/RDY L

Connect a jumper from B08H I (STROBE) to B08N2 (BUS SECTOR PULSE). The
positioner should move to cylinder 105. Confirm this by observing the track scale
indicator.

For the RK05-F drive, select cylinder 5 as foilows:
a.

Connect backboard jumpers from A07TI, A07C2, B07TI, or any available ground pins
to the following points:
A08K2 ODD DRIVE
A08M2
A08LI

CYL ADD 2(4)

A08KI

CYL ADD 0(1)

5
A04VI
b.
10.

SEL RDY L

Connect a jumper from B08H I (STROBE) to B08N2 (SECTOR PULSE). The positionef should move to cylindei 5. Confirm this by observing the track scale indicator.

Monitor the scope for a single pulse followed by data beginning 10,.,.s following the pulse.
This timing pulse may be either positive or negative going. Cylinders 85 and 125 also contain
this pulse, and can be used if 105 is unusable (RK05/RK05-J only).

5-51

11. Expand the sweep time to 10 ~s/div and check that the single pulse occurs 70 ± 12 ~s from
the start of the sweep (Figure 5-25).

INDEX
SECTOR
MARK READ
FROM DISK

INDEX
SECTOR
(AD2R2)

TP3& TP4

SWEEP

10 p.s/div

VERT SENS = 2V/div

I·

70 ms
(±12)

Figure 5-25

-j

M0333

Index/Sector Waveform

12. Ground B08M2 to select the upper head and check for the same pulse tolerances as in Step
11, above. If necessary, adjust R6 on the M7680/M7700 (card position 2) until the average
time for the two pulses is 70 ~s and the 70 ± 12 /-LS individual pulse requirement is maintained. If these requirements cannot be achieved, perform either of the following corrective
actions:
a.

If the time difference of the two timing pulses exceeds 24 /-LS, replace one of the heads to
reduce the difference. Once the difference is within tolerable limits, readjust R6 to
~chieve an average 70 J.Ls between the peaks.

If the average of the peaks cannot be adjusted to 70 /-LS, relocate the sector transducer to
the right (if the average is too high) or to the left (if the average is too low). Readjust R6
to achieve an average 70 /-LS between peaks.

5.4.5.2 2315 CE Pack
NOTE
Do NOT use this procedure with the DEC RK05KAC alignment cartridge; use the procedure from
Paragraph 5.4.5.1.

5-52

1. Unplug the drive ac line cord to remove power.
2. Disconnect the drive interface cable card from the electronic module and install an M930
terminator card in its place.
3. Reconnect the ac line cord to bring the drive up to operating status.
4. Install a 2315 CE test cartridge on the spindle, ensuring that the mating surfaces are clean,
and operate the drive in the run mode for at least 30 minutes. This must be done to allow the
CE cartridge and the drive components to achieve thermal stabilization.
5. Using the WR PROT switch, place the drive in the write protect condition.

6. Set the oscilloscope controls as follows:
vertical
mode
sensitivity
coupling

=
=
=

sweep
A sweep time =
trigger
=
trigger
source
coupling
slope

=
=
=

ADD (invert CHAN 2)
0.2 V/div
dc
10ms/div
normal
external*
ac

*Important: Use a 1:1 probe to connect the scope external trigger input to A02R2 (INDEX).
7. Connect the channell probe to TP3 and the channel 2 probe to TP4 of the G180 card. (Use
10: 1 probes.)
8.

Ensure that the positioner track scale indicates cylinder 00 (Paragraph 5.4.4.2, Step 8).

9. For RK05 or RK05-J drives with 2315 CE Pack, select cylinder 105 as follows:
NOTE
It is also possible to perform the following adjustments using the RK05 Exerciser or simple test
programs.

5-53

Connect backboard jumpers from A07Tl, A07C2, or any available ground pins to the
following points:
A08El

CYL ADD 6(64)

A08Jl

CYL ADD 5(32)

A08Cl

CYL ADD 3(8)

A08Kl

CYL ADD 0(1)
105

A04Vl
b.

SEL/RDY L

Connect a jumper from B08H 1 (STROBE) to B08N2 (BUS SECTOR PULSE). The
positioner should move to cylinder 105. Confirm this by observing the track scale
indicator.

For RK05-F drive with 2315 CE Pack, select cylinder 193 with jumpers as follows:
a.

Connect backboard jumpers from A07T 1, A07C2, or any available ground pins to the
following points:
A08K2 } EVEN DRIVE
A08M2
A08A 1 CYL ADD 7(128)
A08El

CYL ADD 6(64)

A08Kl

CYL ADD 0(1)
ODD DRIVE (193)

A04Vl
b.

SEL/RDY L

Connect a jumper from B08Hl (STROBE) to B08N2 (SECTOR PULSE). The positioner should move to cylinder 193. Confirm this by observing the track scale indicator.

10. Monitor the scope for a single pulse followed by a I-ms burst of data. This pulse may be of
either polarity.
11. Expand the sweep time to 10 ~s/div and check that the single pulse occurs 70 ~s ± 12 ~s
from the start of the sweep (Figure 5-24). This pulse may be of either polarity.
12. Ground B08M2 to select the upper head and check for the same pulse tolerances as Step 11,
above. If necessary, adjust R6 on the M7700 card (card position 2) until the average time for
the two pulses is 70 ~s and the 70 ± 12 ~s individual pulse requirement is maintained. If
these requirements cannot be achieved, perform either of the following corrective actions:
a.

If the time difference of the two timing pulses exceeds 24 ~s, replace one of the heads to
reduce the difference. Once the difference is within tolerable limits, readjust R6 to
achieve an average 70 us between the peaks.

5-54

If the average of the peaks cannot be adjusted to 70 p.s, relocate the sector transducer to
the right (if the average is too high) or to the left (if the average is too low). Readjust R6
to achieve an average 70 p.s between peaks.

5.4.6 Cartridge Receiver Alignment
There are two styles of cartridge receiver in the RK05 and RK05-J. The earlier style is an all-wire
construction mounted on adjustable pivot posts (Figures 5-26 and 5-27). The later style (Figure 5-28)
has a sheet metal "roof' and two rotating plastic clamps on the forward crosswire, and is mounted in a
sheet metal bracket that is completely nonadjustable. The RK05-F with its nonremovable cartridge
has no cartridge receiver as such. Instead, it has a cartridge guide, an access door wedge, and two holddown springs (Figure 5-29). The description in this paragraph applies to the earlier RK05/RK05-J
cartridge receiver.
Prior to shipment of the RK05 Disk Drive, the cartridge receiver is precisely aligned at the factory.
Since it is not necessary to disturb the receiver alignment when performing any of the field maintenance procedures, cartridge receiver alignment is not normally required in the field. However, if the
duckbill, airduct, or cartridge support posts are replaced, the cartridge receiver alignment must be
checked. In addition, the Cartridge-On switch should also be checked for proper operation.
NOTE
The duckbill on later model drives differs slightly
from that on earlier models. If an earlier version
duckbill should be replaced by a later version, the
airduct and cartridge support posts must also be
replaced. Refer to the RK05 Illustrated Parts Breakdown (DEC-RK05-IPB-l) to identify which duckbill
version is being replaced.
1. Slide the drive out of the rack and remove the top and bottom covers.
2. Insert a cartridge into the receiver and close the drive front door.
3. Check for a 0.020 to 0.040-inch clearance (A in Figure 5-26) between the plastic cartridge
case and the receiver rails. Perform this measurement toward the rear of the receiver at a
point where the plastic cartridge case passes over the intersecting receiver rails.
4. If the (A) clearance is incorrect, loosen the pivot post lock nuts and adjust the height of both
posts to obtain the proper clearance. Hold the pivot post at (X) with an adjustable wrench
while loosening and tightening the lock nuts (Y).
5. Lightly tighten the pivot post lock nuts and check the following (Figure 5-27).
a.

Remove the cartridge and ensure that the clearances (B) between the upper receiver
rails and the cartridge channel are equal, and that the receiver rails are as parallel as
possible to the channel.

Push the receiver all the way to one side and ensure that there is a slight clearance (C) of
0.010 to 0.040-inches between the pivot post and the receiver hinge rail. When making
this check, do not push the receiver so hard that the pivot posts twist.

Push the receiver to the left and right, ensuring that the front receiver rail does not
touch either side of the chassis.

5-55

POSITIONER

lC::I:=======::t:========::::1 CARTRIDGE CASE
.020 MIN.
.040 MAX

~LOCK NUTS

CARTRIDGE
RECEIVER

I
rBASEPLATE
CP-0511

Figure 5-26 Cartridge-to-Receiver Clearance

5-56

CARTRIDGE RECEIVER PUSHED
ALL THE WAY TO ONE SIDE
C=.OIO TO .040

CHASSIS

,/11111111111 1 I I I I t / l / / I I

CLEARANCE

~------- +--*---~

BASEPLATE

-------t---------:~2:l~::.::~.,________'!'__ CLEA RAN CE
'11111111 7 II II I 7
CHASSIS

Figure 5-27

i II

Cartridge Receiver Clearances

5-57

CP-0512

7869-16

Figure 5-28 Cartridge Receiver, Newer Models (RK05/RK05-J)

7869-4

Figure 5-29 Cartridge Receiver, RK05-F
5-58

Tighten the pivot post lock nuts and recheck all clearances. There must be clearances at
points (A), (B), and (C); however, it is particularly important that clearances (A) and (C) do
not exceed the limits indicated in Figures 5-26 and 5-27.

7. Check for the following points of contact between the cartridge and the cartridge receiver,
which indicate that the cartridge is properly seated:
a.

Two thin rails (these should either touch evenly or be parallel along the full length of
the cartridge.)

Two cartridge posts

Access door opener bail

Spring at top center of cartridge

Duckbill (lower slot)

Airduct bridge

Airduct foam seal.

8. Check for the following points of clearance between the cartridge and the cartridge receiver,
which indicate that the cartridge is properly seated:
a.

Two fat rails on top of the cartridge

Four crosspoints on the underside of the cartridge

The pivot posts and receiver hinge bail.

The position of the pivot posts determines how the top rails ride on the cartridge and also
determines the bottom clearances of the four crosspoints and the underside of the carriage.
One way to check alignment is to insert a cartridge pack at a slightly cocked angle. The
receiver should guide the pack onto the posts as the door is closing. If a pack will not seat on
the left post, make sure that the top rails of the receiver are n-ot pushing the pack away.
NOTE
Remember that the receiver does not hold, but
merely guides the cartridge. The pack is actually
positioned by the two cartridge posts and the lower
lip of the duckbill. The pack should not rest on or be
tightly squeezed by the cartridge receiver, but should
be able to slide easily.
5.5 SPARE PARTS
Refer to the RK05 Illustrated Parts Breakdown (DEC-RK05-IPB-l) and the H743 Power Supply
T11 ___ .... __ .... _...l

n __ .L_ n ___ l_.-I ______

I'",",~'-"

TTJlltA.,

Tnn

1'\.

________ .... _

~._1

___ ... !P..

__ .t.! __ _

11lu:strau;u ran:s Dn;aKuuwn ~uc\....--n 1't..J-lrD-I) lor pans luenllllcallon.

5-59

5.6 TROUBLESHOOTING
The information in this paragraph will assist the service technician in isolating a failing drive component. This information is intended only as a guide during trouble analysis, and does not cover all
possible malfunctions of any designated area. To eliminate correctly functioning areas of the drive and
arrive at an area of failure, perform the checks described in Paragraphs 5.6.1 through 5.6.4. A basic
knowledge of electronics, primary understanding of DEC logic, and logical deductive reasoning
should then be employed to locate faulty components within the area of failure. Figure 5-30 consists of
a quick-reference flowchart illustrating the checks described in detail in the following paragraphs.
Once the malfunction is diagnosed, corrective maintenance should be performed largely through module swapping. The term module includes those modules listed in the UML (Dwg. No. RK05-0-2), in
addition to the linear positioner, the +5 Vdc regulator, the ± 15 Vdc regulators, and the H604 Servo
Power Amplifier. Failures not attributable to these modules must be repaired at the faulty component
level. If module replacement cannot be accomplished within a practical time period, repair of the
defective modules should be undertaken, with the exception of a defective linear positioner. In all
cases, defective linear positioners should be returned to Digital Equipment Corporation, Maynard,
Mass.
NOTE
The G 180 module should not be used on an extender
module. Faulty G 180s should be replaced in the field,
rather than repaired at the faulty component level, if
the nature of the fault is such that an extender module would normally be required.
5.6.1

Power Supply
1. Open the rear door of the rack and unplug the drive ac line cord.
2.

Extend the drive fully on the slides and remove the top cover.

Disconnect PI (Figure 4-17) from the power supply chassis.

4. Apply power to the drive and check Jl for the following voltages (measured from ground to
the center value of the peak-to-peak ripple):
P!n 1 = + 15 ± 0.75 Vde } 250 m V p_p max ripple of either regulator
pm 2 = -15 ± 0.75 Vdc
pin 3 = +5 ± 1 0.15 Vdc 200 m V p-p max ripple of either regulator
5.

Remove power from the drive and check for shorts between buses.
ATl, BTl = GND
AA2, BA2 = + 5 Vdc } Max allowable ripple voltage seen at these pins on the logic assembly is 200 m V p-p.
AD2, BD2 = + 15 VdC} Max allowable ripple voltage seen at these pins on the logic assembly is 250 mV p-p.
AB2, BB2 = -15 Vdc

Reconnect PI and apply power to the drive ..

Measure the +5, + 15, and -15 Vdc at the buses as indicated in Step 5, above. The tolerances
should be the same as those in Step 4, above.

8. Check for approximately 30 Vac at A04El.
9,

Remove power from the drive.
5-60

YES

DATA TESTING
CP-0533

Figure 5-30 Troubleshooting Flowchart

5-61

5.6.2

Controls and Indicators
1. Check that all modules are present and in their correct locations (Dwg. No. RK05-0-2).
2. Apply power to the drive and check that:
a.

the PWR and LOAD indicators are lit and that the WT and RD indicators are OFF.
(WT and RD can be checked while formatting a cartridge during the diagnostic
exercise.)

the door unlocking solenoid is energized.

the blower is operating.

3. Press the WT PROT switch and check that the WT PROT indicator lights. (The drive
should power-up with WT PROT off.)
5.6.3

Mechanical Checks
1. Open the rear door of the rack and unplug the drive ac line cord.
2. Extend the drive fully on the slides, and remove the bottom covers.
3. Tape the door-locking bar (located behind the front bezel) in the down position (Figure 531). This permits the drive front door to be opened and shut without power being applied.
(This does not apply to the RK05-F.)
4. Install a test cartridge in the drive.
CAUTION
Do not attempt to cycle up the drive with the locking
bar disabled.
5. Check the following to ensure that the cartridge is seated properly:
a.

Ensure that there is a clearance between the lip on the metal disk hub and the sector
transducer slot (Figure 5-32).

The airduct foam seal fits snugly to the bottom of the cartridge case.

The cartridge case rests securely on the front cartridge support posts. (No gaps hetween
the cartridge case and the support posts shoulders.)

6. Rotate the spindle pulley by hand and check that:
a.

the disk surface does not touch the duckbill.

there is no scraping or rubbing sound within the drive.

the drive belt is not stretched or worn.

5-62

DOOR LOCKING BAR

7553-5

Figure 5-31

AIRDUCT FOAM SEAL

Door Locking Bar Location

SECTOR TRANSDUCER

CARTRIDGE SUPPORT POSTS

Figure 5-32

Cartridge Seating Elements

5-63

Remove the tape from the door-locking bar and apply power to the drive (if RK05 or RK05J Disk Drive).
Place the RUN/LOAD switch in the RUN position and check that:

5.6.4

the PWR indicator is lit.

the disk is rotating and there is still no rubbing sound from within the drive.

after approximately 8 seconds, the heads load.

the RDY and ON CYL indicators are lit.

the door is now locked.

Place the RUN/LOAD switch in the LOAD position and check that the door unlocks when
the LOAD light comes on.

Remove power from the drive.

Electronic Checks
1. If possible, perform the Dynamic Off-Line Servo System Timing Checks (Paragraph
5.4.2.1). If there is any question about the drive operating well enough to accomplish the
dynamic servo timing checks, perform the Static Tests and Adjustments (Paragraph 5.4.2.2).

NOTE
When attempting the preceding checks, ii the drive
does not start or stop correctly, refer to the Start
Flowchart (Figure 4-2) or the Stop Flowchart (Figure 4-3) for areas of possible malfunction. If the drive
starts properly but does not execute a Seek or
Restore command correctly, refer to the Seek Flowchart (Figure 4-4) or the Restore Flowchart (Figure
4-5).
2.

Verify that the heads are correctly aligned (Paragraph 5.4.4).

3. Check the Index/Sector Timing (Paragraph 5.4.5).
4.

Remove all jumpers and configure the drive for normal operation.

Ensure that spindle brushes are mating properly and that the ground strap between the
chassis and the baseplate is secure; otherwise, random data errors may result.

6. Inspect the logic assembly for bent or shorting pins.
7. Check the power supply voltages.
8.

Run the appropriate diagnostic tests to exercise the remaining portions of the drive.

5-64

I
I

I
I
I
I
I
I
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RKOS/RKOSJ/RKOSF DISK DRIVE
MAINTENANCE MANUAL
EK-RKSJF-MM-OOI

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