Video Board Parts Layout
Display PCB Assembly — Commodore Business Machines, Inc.'s component-placement drawing for the Commodore PET 2001 display assembly, scanned at 400 dpi. The board outline is shown with the copper pattern in grey and a reference designator and a value printed against every fitted position.
"Video board" is this wiki's word, not Commodore's. Commodore calls it the display assembly, and it is the machine's power supply as well as its monitor.
This is the most immediately useful of the PET display documents on this wiki, because it is the one that lets you identify a part without tracing the schematic: point at a can on the board, read the designator and the value off the drawing.
 | The display assembly is the PET's power supply as well as its monitor. Mains voltage is present on it whenever the machine is plugged in, the CRT anode runs at roughly +10 kV from flyback T2, and C1 is a 4700 µF reservoir that stores real energy. Read CRT Discharge Procedure before working on this board. |
What the drawing settles
[edit | edit source]VR1 is a 7812. The position is marked "VR1 7812 UC" inside heatsink H1. Commodore's parts list says only "voltage regulator, part 901527-01" — this drawing is where the actual device type is recorded, and it confirms that the display assembly's regulated output is +12 V.
C22 and C27 are 3.3 µF, not 33 µF. Both positions are marked "3.3 µF 200 V OR 160 V". Commodore's parts list prints that line as "33 µF/200 V or 4.7 µF/250 V", and the display schematic marks them 3.3 µF. Two drawings against one parts-list line, and the listed 4.7 µF alternative only makes sense beside 3.3 µF. This drawing also adds the 160 V alternative rating, which the parts list does not give.
Q14 has a documented substitution. The main drawing marks Q14 as MJE-13006 in heatsink H2; an inset headed Detail of substitution TR. Q14 and heat sink H2 covers fitting a TIP-55A instead, and instructs that the collector lead is cut off and the screw head connected to the PCB pattern by solder — the TO-220 tab becomes the collector connection. Two #6-32 Phillips screws, two #6-32 hex nuts and two lock washers per device.
The jumper wires are marked. Several links on the board are flagged with a symbol and a legend reading "jumper wire". They are factory links, not repairs, and not missing components.
Values printed on the drawing
[edit | edit source]| Position | Value as printed |
|---|---|
| C1 | 4700 µF 25 V |
| C3 | 47 µF 16 V |
| C9 | 1 µF 25 V |
| C12, C13 | 47 µF 16 V |
| C14 | 0.15 µF |
| C15 | 470 µF 16 V |
| C16 | 0.1 µF |
| C19 | 0.01 µF |
| C20, C30 | 220 pF |
| C22, C27 | 3.3 µF 200 V or 160 V |
| C23 | 220 µF |
| C24 | 0.001 µF 200 V |
| C25 | 0.022 µF 200 V |
| C28 | 10 µF N.P. |
| C29 | 820 pF |
| CR7 | 33 V 1 W zener |
| CR16 | 1N4148 |
| CR17, CR18 | 1N4935 |
| CR19–CR22 | 4 × 1N5402 — the mains bridge |
| L1 | Miller 5250 |
| L2 | Miller 4632 |
| Q9 | TIP29 |
| Q10 | TIP30 |
| Q14 | MJE-13006 (TIP-55A substitution documented) |
| R9 | 100 k |
| R20 | 1 M |
| SG1, SG3 | spark gap, 0.01 µF 1.5 kV |
| SG4 | spark gap, 0.75 pF |
| T1 | Marvel M594 A1A |
| T2 | GI 294-7746 flyback |
| VR1 | 7812 UC |
The rails marked on the drawing are +12 V and −12 V.
What it does not contain
[edit | edit source]No circuit — this is placement only. No test points or waveforms; those are on Video Board Schematic. No Commodore part numbers; those are in Video Board Parts List (1 of 3). Nothing about the main logic board, which has no equivalent placement drawing on this wiki.
Related pages
[edit | edit source]- Video Board Schematic · Video Board Schematic (Rev 2, 320032) · Video Board Schematic (Rev 3, 320033)
- Video Board Parts List (1 of 3) · Video Board Parts List (2 of 3) · Video Board Parts List (3 of 3)
- Schematic Notes for Video Board
- Commodore PET 2001 Capacitor Replacement Guide · Commodore PET 2001 Service Documentation · CRT Discharge Procedure · Capacitor Failure Symptoms
Download: video-layout.gif