A person in need of my help of which i have already repaired several devices has contacted me and asked if i could make a repair of one of his Commodore PET with two different trouble.

• The first fault was black screen on power up, meaning no image was displayed.
• The second fault that occurred after a couple of days was a raster video distortion of the CRT monitor accompanied by a smell of burning (see photo)

The first fault was solved by replacing the UD7 ROM (901465-02) with an eprom (2532), the correct functioning test could be done by connecting the LCD monitor that i use for repairs via a video adapter.

The second fault was brilliantly resolved by replacing the voltage regulator installed on the pcb monitor, a 7812 which on the pin output did not always return 12v but rather a mix between 3v, 6v, 10v.

I also removed some pieces of foam rubber (see photo) which due to the glue used has damaged the back of the monitor PCB leaving obvious traces of corrosion and a black sticky stain that i have removed.

I also rebuilt a missing pin of the ROM UF14 (901447-10) that someone had thought to fix in a very rough way (see photo)

Gallery of the repair:

Download:

• BASIC 2 - UD7 ROM (901465-02) (632)