Commodore PET 2001 Service Documentation

Four Commodore service documents for the Commodore PET 2001 are hosted here: a parts list and a schematic for each of the two circuit boards, the main logic assembly and the display assembly. They cover both boards at component level, and they are the source for the values on Commodore PET 2001 Capacitor Replacement Guide. The mains transformer and the logic supply's reservoir capacitor are mounted in the case and appear in none of the four; PET-Shack's third-party bundle, below, has a wiring drawing for them.

Parts lists

8K Main Logic Assembly Parts Cross Reference: the system board's components by reference designator, description and Commodore part number, three pages. It omits the four +5 V regulators VR3-VR6, which are on sheet 2 of the schematic.
Display Assembly Component Cross Reference: the same for the 9-inch monitor board, which makes its own +12 V from a separate transformer winding.

Schematics

Main logic schematic, assembly 320008: three sheets. Sheet 1 is drawing 320130, circuitry common to all PET computers; sheets 2 and 3 are drawing 320026 and are specific to assembly 320008. Sheet 2 includes the board's power section: connector J8, rectifiers CR1-CR3 and regulators VR3-VR6 with test points TP1-1 to TP1-4.
Schematic, Service, Display Circuit: the monitor board, with the oscilloscope settings for the waveform photographs on a second sheet.

The four original board assemblies

Commodore's note on sheet 3 of the main logic schematic records that all component locations are the same on all four boards; only the fitted components differ, and the identifying board number is silkscreened in the upper left corner.^[1]

**Original PET 2001 ("static") board assemblies**
Assembly	ROMs	RAM	Schematic
320008	6540	6550	320026
320081	2316B	6550	320082
320132	6540	2114	320130
320137	2316B	2114	320135

All four are variants of the original static board. The later 2001-N, 3000 and 4000 dynamic system board is a different design and is not covered by these documents; for those machines see Commodore PET 4000 Series.^[2]

What these documents establish

The only aluminium electrolytics on the main logic board are C7-C10, 47 µF 16 V, on the outputs of the four regulators.^[1] C5, C11, C12 and C13 are 1 µF 25 V tantalums; C15–C49 are 0.1 µF ceramics.^[3]
The display assembly's reservoir is C1, 4700 µF 25 V, feeding the 7812 regulator VR1.^[4]
The main logic board makes its own supplies: CR1 and CR2 rectify a 15.7 V AC centre-tapped winding into the +9 V unregulated rail, and VR3-VR6 each make +5 V for part of the board. The parts cross-reference does not list the regulators.^[1]^[3]
The display assembly generates +12 V, a +85 V boost rail, −30 V and about +10 kV for the CRT anode.^[5]
The master crystal Y1 is 8 MHz.^[1]

The full drawing set, sheet by sheet

The same documents are also held here as individual high-resolution sheets, for citing one drawing at a time.

Main logic assembly

System Board Parts List (1 of 3): Main Logic Assembly Parts Cross Reference, sheet 1: capacitors, diodes, transistors, connectors and resistors with Commodore part numbers. Only C7-C10 are aluminium electrolytics.
System Board Parts List (2 of 3): sheet 2, the IC cross-reference: 6502 at UF3, 6520 PIAs at UB8/UG8, 6522 VIA at UA5, and the 6550 and 2114 RAM lines printed against the same eighteen positions, which is how Commodore expressed the difference between the board assemblies.
System Board Parts List (3 of 3): sheet 3, the remaining ROMs and the socket types. Records a revised UH1 ROM (6540-019 / 2316B-09, parts 901439-09 / 901447-09) and shows that the 6540 is a 28-pin part and the 2316B a 24-pin part.
2001 Main Logic Assembly: a later issue of the same list as one PDF, on Commodore's Santa Clara letterhead, with numbered lines and dealer prices. The three images above are the earlier Palo Alto issue. The file is byte-identical to File:Commodore PET 2001 Main Logic Assembly Parts List.pdf.

The set has a component-placement drawing for the display assembly but none for the main logic board.

Main logic schematics, by board assembly

Sheet 1 of every set is the same drawing, #320130, Circuitry common to all PET computers. Sheets 2 (Memory Section) and 3 (Video Logic) are the board-specific drawings.

Board	Complete set	Sheet 2, memory section	Sheet 3, video logic
320008	Schematic 320026 (Complete, Board 320008)	Schematic 320026 (Sheet 2 of 3, Board 320008)	Schematic 320026 (Sheet 3 of 3, Board 320008)
320081	Schematic 320082 (Complete, Board 320081)	Schematic 320082 (Sheet 2 of 3, Board 320081)	Schematic 320082 (Sheet 3 of 3, Board 320081)
320132	Schematic 320130 (Complete, Board 320132)	Schematic 320130 (Sheet 2 of 3, Board 320132)	Schematic 320130 (Sheet 3 of 3, Board 320132)
320137	Schematic 320135 (Complete, Board 320137)	Schematic 320135 (Sheet 2 of 3, Board 320137)	Schematic 320135 (Sheet 3 of 3, Board 320137)

On sheet 2 the RAM chips for addresses 1000–1FFF are marked with an asterisk, and a handwritten note beside the title block reads "All ckts marked * are for 8K machine only".

Display assembly

Commodore calls this the display assembly; the page titles below call it the "video board". It takes 16.2 V AC on its 2-pin header J2 and carries its own bridge, the 4700 µF reservoir C1, the +12 V regulator VR1, the −30 V and +85 V rails and the flyback.^[5]^[4]

Video Board Parts Layout: Display PCB Assembly, the component-placement drawing, with a designator and a value against every fitted position, so a part can be identified without tracing the circuit. It marks VR1 as a 7812 and C22/C27 as 3.3 µF, and documents the TIP55A substitution for Q14.
Video Board Schematic: Schematic, Service, Display Circuit, with fourteen waveform photographs and five service notes (R20 mounts perpendicular for screwdriver adjustment; R9 is at the rear on a 2-inch shaft; Molex 09-64-1021 and 09-64-1061 board connectors; parenthesised numbers are the DOK flyback version).
Schematic Notes for Video Board: the oscilloscope settings for those fourteen photographs, volts and time per division for each, and one absolute amplitude, picture 9 at 11.6 V peak. The photographs cannot be read without it.
Video Board Schematic (Rev 2, 320032): Commodore drawing #320032 rev A, Display Schematic, drawn 3-9-76, last revised 6-15-77.
Video Board Schematic (Rev 3, 320033): Commodore drawing #320033 rev P, size D, Schematic, Display Circuit, engineering-approved 29 June 1978, next assembly #320012.
Video Board Parts List (1 of 3) · Video Board Parts List (2 of 3) · Video Board Parts List (3 of 3): Display Assembly Component Cross Reference, items 1–70 with Commodore part numbers, including the yoke assembly (320078) and the bare PCB (320084-02).

The "Rev 2" and "Rev 3" in those titles are not Commodore's: 320032 and 320033 are different drawing numbers with their own revision marks, A and P.

Other PET material hosted here

Schematic 320130 (Sheet 1 of 3, Static PET): Commodore drawing 320130 sheet 1, PET Computer Main Logic, circuitry common to all PET computers, as a single image. The 6502 at F3, both 6520 PIAs, the 6522 VIA, the three MC3446 IEEE-488 transceivers at A7-A9, the LM555 timer (labelled UDE9), the cassette-motor drivers on the +9 V unregulated rail and the keyboard pull-ups. The board's +5 V regulators are on sheet 2.
PET Shack Service Bundle: a 37-page third-party compilation sold by PET-Shack (P.S. Software House) of Mishawaka, Indiana. Not Commodore documentation, but it has things Commodore's documents here do not: the console wiring drawing (power switch, 1.8 A fuse, transformer windings of 16.2 V AC to the monitor and 15.7 V AC centre-tapped to the logic board, and a 23,000 µF 15 V capacitor), an errata sheet against the schematics, the cassette deck circuit, a video monitor schematic, and data sheets for the 6550, 6540, 2114, 2316, the Synertek 6502, 6520 and 6522, and the MC3446.

Related pages

Commodore PET 2001 · Commodore PET 2001 General Maintenance · Commodore PET 2001 Troubleshooting · Commodore PET 2001 Capacitor Replacement Guide
Commodore PET 4000 Series Technical Manual: P/N 990438, with parts lists and schematics for the universal dynamic PET boards 8032090 and 8032080 (8032, 4032, 4016 and SuperPET 9000 builds) and for the earlier dynamic PET board 320351

References

↑ ^1.0 ^1.1 ^1.2 ^1.3 Commodore Business Machines, PET Computer Main Logic schematic, drawings 320130 (sheet 1) and 320026 (sheets 2–3), for board assembly 320008. Hosted here as File:Commodore PET 2001 Main Logic Schematic (320008).pdf. Sheet 3 carries Commodore's note that component locations are common to assemblies 320008, 320081, 320132 and 320137.
↑ zimmers.net Commodore PET schematics index. Directory listing that separates the original 2001 static board (folder 2001, with the four assembly schematics) from the 2001N dynamic board.
↑ ^3.0 ^3.1 Commodore Business Machines, 8K Main Logic Assembly Parts Cross Reference for the PET 2001. Hosted here as File:Commodore PET 2001 Main Logic Assembly Parts List.pdf. Gives every component on the system board by reference designator, description and Commodore part number.
↑ ^4.0 ^4.1 Commodore Business Machines, Display Assembly Component Cross Reference for the PET 2001. Hosted here as File:Commodore PET 2001 Display Assembly Parts List.pdf. Numbered list of every component on the monitor and supply board.
↑ ^5.0 ^5.1 Commodore Business Machines, Schematic, Service, Display Circuit for the PET 2001, with the supplementary sheet of oscilloscope settings. Hosted here as File:Commodore PET 2001 Display Circuit Schematic.pdf. Shows CR19–CR22, C1, VR1, the +85 V boost and −30 V rails, the flyback T2 and the +10 kV anode supply, and the deflection yoke figures.

[msch-1] 1.0 ^1.1 ^1.2 ^1.3 Commodore Business Machines, PET Computer Main Logic schematic, drawings 320130 (sheet 1) and 320026 (sheets 2–3), for board assembly 320008. Hosted here as File:Commodore PET 2001 Main Logic Schematic (320008).pdf. Sheet 3 carries Commodore's note that component locations are common to assemblies 320008, 320081, 320132 and 320137.

[zim-2] zimmers.net Commodore PET schematics index. Directory listing that separates the original 2001 static board (folder 2001, with the four assembly schematics) from the 2001N dynamic board.

[mla-3] 3.0 ^3.1 Commodore Business Machines, 8K Main Logic Assembly Parts Cross Reference for the PET 2001. Hosted here as File:Commodore PET 2001 Main Logic Assembly Parts List.pdf. Gives every component on the system board by reference designator, description and Commodore part number.

[disp-4] 4.0 ^4.1 Commodore Business Machines, Display Assembly Component Cross Reference for the PET 2001. Hosted here as File:Commodore PET 2001 Display Assembly Parts List.pdf. Numbered list of every component on the monitor and supply board.

[dsch-5] 5.0 ^5.1 Commodore Business Machines, Schematic, Service, Display Circuit for the PET 2001, with the supplementary sheet of oscilloscope settings. Hosted here as File:Commodore PET 2001 Display Circuit Schematic.pdf. Shows CR19–CR22, C1, VR1, the +85 V boost and −30 V rails, the flyback T2 and the +10 kV anode supply, and the deflection yoke figures.

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