Diagnosing a Commodore PET video fault from one photograph

• Tynemouth Software writes about an owner who had initially made contact saying they had a PET 2001, and there was no video output, and they wondered if bad ROM or RAM could cause that and would a PET ROM/RAM fix the issue? • After some probing around, they found the 74177 at D6 was at fault, and replacing that give video sync and a screen full or random characters. • Time for a ROM/RAM board. • One was order and fitted. • Normally that would cure the issue, but in this case, it did not. • I was sent this photo of the screen (above) .

Article Summaries:

• Tynemouth Software writes about an owner who had initially made contact saying they had a PET 2001, and there was no video output, and they wondered if bad ROM or RAM could cause that and would a PET ROM/RAM fix the issue? After some probing around, they found the 74177 at D6 was at fault, and replacing that give video sync and a screen full or random characters. Time for a ROM/RAM board. One was order and fitted. Normally that would cure the issue, but in this case, it did not. I was sent this photo of the screen (above) . … I wrote quite a lot of that in the email response to the owner, with

Sources:

• https://blog.adafruit.com/2026/02/17/diagnosing-a-commodore-pet-video-fault-from-one-photograph/