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Document:	TU78 Subsystem Pocket Service Guide
Order Number:	EK-0TU78-PS
Revision:	CN1
Pages:	4
Original Filename:

OCR Text

EK-0TU78-PS-CNI1

Technical Change Nofice
TU78 Subsystem
Pocket Service Guide

EK-0TU78-PS-002

PURPOSE

C.1

The purpose of this addendum is to document two major
changes to the TU78 power supply.

I. New configuration of the power transformer voltage
taps (Paragraph C.2).

2. Additional fuse panel and fuses (Paragraph C.3).
NOTE

If you have the new fuse panel you may not
necessarily have the new power transformer

voltage tap configuration. Compare the figures
and tables in this addendum to your tape drive
to determine what modifications you have.

C.2 POWER TRANSFORMER VOLTAGE TAPS
All drives now being shipped from the vendor have a new
configuration for the power transformer voltage taps. The
new configuration begins with units having a serial number of about 12500 and higher.

Table C-1 shows the configuration of early models of the
power transformer voltage taps. Table C-2 shows the new
configuration for later models. Using Figure C-1, find the
power transformer terminal strip. Compare this with
Tables C-1 and C-2 to determine what configuration you
have.

C.3

FUSE PANEL AND FUSES

Additional fuses have been added to the power supply to
prevent component failures. Figure C-2 shows the early
type of fuse panel. Table C-3 shows the voltage ranges
that should be present at these fuses.

Figure C-3 shows the new fuse panels. Table C-4 shows

the voltage ranges that should be present at these fuses.

114

APPENDICES
POWER TRANSFORMER

TERMINAL STRIP
TERMINAL NO. 1

@/0000000000000

@%MINAL NO. 9

SHR-0458-85

Figure C-1

Table C-1

Location Of Power Transformer
Terminal Strip

Primary Power Connections (Early Models)
Brown Wire and

Input Voltage

Blue Wire

White/Red Wire

198 - 205

TB1-4

TBI1-7

206 — 215

TBI1-3

TB1-7
TB1-8

216 — 225

TB1-4

226 — 235

TBI1-3

TBI1-8

236 — 245

TB1-4

TBI1-9

246 — 255

TBI1-3

TBI1-9

115

APPENDICES

Primary Power Connections (Later Models)

Table C-2

Brown Wire and

Input Voltage

Blue Wire

White/Red Wire

198 - 214
215 - 224

TB1-4
TBI1-3

225 - 234
235 - 245

TB1-4
TB1-3

TB1-8
TB1-8
TB1-9
TB1-9

Fo6

o] [e] [e] [e]l [e

I I O O e O e
o] To] [ef [of Teof

ll-lm

]
o] Lo

POWER SUPPLY PANEL

C—"C
Ch

MA-3675

SHR-0459-85

Figure C-2

Table C-3

Power Supply Fuse Panel (Early Models)

Power Supply Voltage Readings (Early Models)

Type

Measured Voltage (dc)
Minimum Nominal Maximum

Circuit
Fuse Function
Fl

+12°V

7 A FB

+9.5

+10.5

+I11.5

+24 V

5AFB

24V

+22.0
-22.0

+24.0
-24.0

+26.0
-26.0

+36 V (C) 20 A FB
36 V(C) 20 AFB
+36 V (T) 20 A FB
+36 V (S) 20 A FB

+35.0

4375

+40.0

-35.0

-37.5

-40.0

+38.0

+40.0

+42

+38.0

+40.0

+42.0

F5
Fo6

AFB

116

APPENDICES
F10

F11
1

e
oo

Fi2

F13

F14

o] [o] [
SI N o B

o] [e]
N

o
DROEG
\

F B[R

------,'l

e e
TR

e
E

R
@

POWER SUPPLY PANEL

MA-3675

SHR-0460-85

Power Supply Fuse Panel (Later Models)

Figure C-3

Table C-4

Power Supply Voltage Readings (Later Models)

Circuit
Type
Fuse Function

Measured Voltage (dc)
Minimum Nominal Maximum

FI. 412V
F2 424V
F3 -24V
V(C)
F4 +36
V(C)
F5 -36
F6 +36 V(T)
F9 +36V(S)
F10 436 V(T)
V(S)
FI1 -36

ASB
30
ASB
30
ASB
10
10ASB
15ASB
15ASB
20AFB
20 A FB
20A FB

+95
+220
-22.0
+350
-350
+38.0
+38.0
+38.0
-38.0

+10.5
4240
-24.0
+37.5
-37.5
+40.0
+40.0
+40.0
-40.0

+I11.5
+26.0
-26.0
+40.0
-40.0
+42.0
+42.0
+42.0
-42.0

V(C)

20A FB

-35.0

-37.5

-40.0

F12 36 V(T)
F13 +36 V(C)
F14 -36

20A FB
AFB
20

-38.0
+35.0

-40.0
+37.5

-42.0
+40.0