Schematic Notes for Video Board
Schematic Notes for Video Board holds Commodore's Supplement to Schematic for Display Circuit, a single typed page on Commodore Business Machines letterhead (901 California Avenue, Palo Alto, California). It gives the oscilloscope settings for the fourteen waveform photographs printed on the Commodore PET 2001 display circuit schematic, held here as Video Board Schematic. The sheet opens: "The following data should accompany each of the photographs". The scan is notes-2.gif from the PET 2001 schematics directory at zimmers.net, which describes it as "Notes to go with video board schematic".[1]
The settings, as printed
| Picture | Vertical | Timebase | Note |
|---|---|---|---|
| 1 | 1 V | 5 ms | |
| 2 | 5 V | 2 ms | |
| 3 | 1 V | 20 µs | |
| 4 | 10 V | 0.5 ms | |
| 5 | 0.2 V | 0.2 ms | |
| 6 | 5 V | 5 ms | |
| 7 | 0.5 V | 5 ms | |
| 8 | 0.5 V | 20 µs | |
| 9 | 0.5 V | 20 µs | 11.6 V peak |
| 10 | 0.2 V | 20 µs | |
| 11 | 5 V | 20 µs | |
| 12 | 1 V | 20 µs | |
| 13 | 20 V | 20 µs | |
| 14 | 5 V | 5 ms |
Commodore writes each line as a voltage and a time ("1V 5 mil sec", "1V 20 micro sec") without saying "per division". Picture 9 is the only one with an amplitude against it, "11.6V peak".
What it does not contain
The page does not say where each photograph was taken. The numbered test points, circled 1 to 14, are marked on the display circuit schematic itself. The page has no component values, rail voltages or fault information.
 | The CRT anode runs at about +10 kV from flyback T2 on the display board, and the tube holds its charge after power-off. Read CRT Discharge Procedure before working on the display board.[2] |
Related pages
- Video Board Schematic, the drawing these settings belong to
- Video Board Parts Layout
- Video Board Parts List (1 of 3)
- Commodore PET 2001 Service Documentation
- Commodore PET 2001 Troubleshooting
Download: notes-2.gif
References
- ↑ /pub/cbm/schematics/computers/pet/2001/—link(accessed 2026-10-01)
- ↑ Commodore Business Machines, Schematic, Service, Display Circuit, hosted as File:Video-1.gif. Shows the fourteen waveform photographs and the circled test points 1-14, the +10 kV output of flyback T2, bridge CR19-CR22, reservoir C1 4700 µF 25 V and regulator VR1 (78/12) for +12 V.
