Schematic 320082 (Complete, Board 320081)
Commodore drawing #320082, the complete three-sheet main logic schematic for PET 2001 board assembly #320081, Commodore Business Machines, Inc., Palo Alto, California. Three A-size sheets, scanned at 400 dpi.
Assembly 320081 is the static PET 2001 board fitted with 2316B ROMs and 6550 RAM.
The three sheets
[edit | edit source]| Sheet | Drawing number in the title block | Title | Also on this wiki as |
|---|---|---|---|
| 1 of 3 | #320130 — not #320082 | PET Computer Main Logic — "Circuitry common to all PET computers" | Schematic 320130 (Sheet 1 of 3, Static PET) |
| 2 of 3 | #320082 | PET Computer Main Logic — Memory Section, pertaining to board assembly #320081 | Schematic 320082 (Sheet 2 of 3, Board 320081) |
| 3 of 3 | #320082 | PET Computer Main Logic — Video Logic, pertaining to board assembly #320081 | Schematic 320082 (Sheet 3 of 3, Board 320081) |
Sheet 1 is the same drawing in all four sets. Its title block reads #320130 whichever board's PDF you open, which is why this wiki holds only one copy of it. Sheets 2 and 3 are the board-specific drawings and carry #320082.
The four static board assemblies
[edit | edit source]| Board assembly | ROMs | RAM | Drawing number for sheets 2–3 |
|---|---|---|---|
| 320008 | 6540 | 6550 | 320026 |
| 320081 | 2316B | 6550 | 320082 |
| 320132 | 6540 | 2114 | 320130 |
| 320137 | 2316B | 2114 | 320135 |
Commodore's note is printed on sheets 2 and 3 of every set: "All locations are same on all boards; only the specific components will differ on boards numbered 320132, 320081, 320137, 320008. The identifying board number is in upper left corner." So a component location read off one of these drawings is valid for any static PET 2001 board; only the fitted part changes.
What these sheets contain
[edit | edit source]- Sheet 1 — the 6502 at UF3, both 6520 PIAs (UB8, UG8), the 6522 VIA (UA5), the three MC3446 IEEE-488 transceivers at UA7–UA9, the LM555 retrace timer, the cassette interface with its TIP29 motor drivers and 7.2 V zeners, and the keyboard matrix pull-ups. No regulator — the board takes +5 V and +9 V unregulated from elsewhere in the machine.
- Sheet 2, Memory Section — the ROM and RAM array for this assembly specifically, which is what distinguishes the four boards.
- Sheet 3, Video Logic — character generator, video timing and the display output.
Some circuits on sheets 2 and 3 are marked with an asterisk and annotated "all ckts marked * are for BC machine only" — the business-keyboard variant.
What these sheets do not contain
[edit | edit source]- No parts list. Values appear on the drawing where the drawing carries them. For the full component list with Commodore part numbers see System Board Parts List (1 of 3) and Commodore PET 2001 Service Documentation.
- No power supply and no display circuitry. The mains transformer, the rectifiers, the 4700 µF reservoir and the flyback are all on the display assembly — see Video Board Schematic and Video Board Parts List (1 of 3).
Each sheet carries Commodore's 1970s trade-secret notice down the left edge. It is of historical interest only.
Related pages
[edit | edit source]- Commodore PET 2001 · Commodore PET 2001 Service Documentation · Commodore PET 2001 Capacitor Replacement Guide · Commodore PET 2001 General Maintenance · Commodore PET 2001 Troubleshooting
- The other three board sets: Schematic 320026 (Complete, Board 320008) · Schematic 320130 (Complete, Board 320132) · Schematic 320135 (Complete, Board 320137)
Download: 320081.pdf