Category Archives: Commodore

Commodore 4032.

Pet4032-StartUpA friend at work, knowing that I was interested in retro computing, arrived one day with this splendid example of a Commodore 4032.. Sadly when I powered it up I only got a “Bingley beep” sound but there was at least some signs of life.

I moved around the board with a scope and found the clock looked good, as did the horizontal and vertical video signals.

More searching found that the _INT_ line to the 6502 was low. I reasoned that it should be mostly high. The 6520 PIA controller driving the IEEE port is connected to that line and as I didn’t need IEEE at the moment I pulled the chip out. Power up and Bingo! now running.Pet4032-J7-pin5


I replaced the 6520 and all is now well.