I bought a batch of chess computer service manuals from a retailer in New Zealand in 2018. They typically include the following information -

1. Schematic and Block Diagrams
2. PCB Layout - Component and soldering sides.
3. Parts List
4. Testing Procedures
 some also include
5. Troubleshooting
6. Chip information including Pin Assignments


Below is the list of service manuals available. Click for the pdf ->

Mephisto
Exclusive (Saitek Chinese Board)
LCD 6 Generation Module
Senator
Montreux
Solar Star
Atlanta


Novag
Chess Printer
Quartz Chess Clock
Micro III (841)
Constellation Junior (852)
Constellation Forte (864)
VIP (872)
Solo (873)
Super Expert A (878)
Super Forte C (901)
Scorpio (909)

Saitek
Atlas
MK12 Trainer
Risc 2500
President
Travel Champion 2100
PC Auto Chessboard
GK 2100
Capella
Centurion



Further service manuals in pdf format can also be found here -
https://schach.computer/schaltplaene/
These include service manuals for Saitek Maestro, Analyst and Brute Force modules and OSA interfaces plus a few other Saitek/Mephisto models.