This 8-Bit Commodore PET Was Hard to Fix
Over on [Ken Shirriff]’s blog is a tricky Commodore PET repair: tracking down 6 1/2 bad chips. WARNING: contains 8-bit assembly code.
The Trinity of 1977 which started the personal computer revolution were the Apple II, the Commodore PET, and the TRS-80. In this project it’s a failing Commodore PET which is being restored.
In the video below the break you can see [Ken Shirriff] and [CuriousMarc] team up to crack this tough nut. Resolving the various issues required a whole heap of software and equipment. Most notably a Keysight DSOX3104T oscilloscope, a Retro Chip Tester Pro, an old Agilent 1670G logic analyzer (this thing is rocking a 3.5″ floppy disk drive!), an old Agilent 54622A oscilloscope (also rocking a floppy drive!), a Data I/O 29B Universal Programmer With UniPak 2 insert, and the disassembly software Ghidra.
In the end there were 6 (and a half) bad chips which needed to be discovered and then replaced. This project is a reminder that it’s nice to have the right tools for the job!
If you’re interested in the Commodore PET you might like to read A Tricky Commodore PET Repair And A Lesson About Assumptions or Tracking Satellites With A Commodore PET.
