LG31 Printer

This technical manual provides comprehensive information for servicing the LG31 300 LPM Line Matrix Printer. It covers the printer's functions, diagnostics, adjustments, and part replacement procedures.

The document begins with an overview of the printer's general description, major components (control panels, print mechanism, electronics), and key features. These features include support for U.S. ASCII 7-bit and 8-bit codes, an Electronic Vertical Forms Unit (EVFU), automatic self-diagnostics, and dot matrix printing using three print actuator modules. It details character formation in data processing and near letter quality modes, ribbon cartridge specifications, paper handling via tractors, and various printing capabilities like bolding, bar codes, and multiple character sets.

The manual then delves into the theory of operation, explaining the enclosure, interlock switches, cooling fans, and the mechanical print system, including the paper drive, ribbon assembly, and print actuator assembly. A significant section describes the printer's electronics, outlining the roles of various Shuttle Matrix System boards (SCPI, SMDP, SMSM, SMIM, SMIH, SHAD, SMMC) and the power supply components (SPSX, SPSM, SPSR, SPSD).

Further chapters detail controls and indicators (inner and outer control panels, modes of operation, forms setup procedures), printer and host configuration (factory settings, power-up parameters, and control strap settings for host interfaces like VAX/VMS, RSX, RT-11, RSTS/E).

A substantial part of the manual is dedicated to troubleshooting, covering diagnostic self-tests, error codes, printer initialization (from the front panel or a locked-up state), mechanical fault finding (paper feed, printing mechanism, vibration), and power supply testing. Extensive removal and replacement procedures for Field Replaceable Units (FRUs) are provided for numerous components, from covers and motors to logic and power supply boards. Finally, print quality adjustment procedures are outlined, using test patterns to fine-tune aspects such as shuttle movement amplitude, vertical and horizontal timing, and intermodule gaps. Appendices include lists of LG31 system fuses, control codes, a summary of printed circuit boards, and interconnection diagrams.