Hi Gang, I'm looking for Commodore PET schematics, and any helpful info on troubleshooting a PET. The machine in question is a SuperPET 9000. This is basically a PET 4032 with an extra pair of boards added that allows a 6809 processor. I have two machines, one is fully functional, and one does not run on the "6502" setting (works on the 6809 setting). I also have a working 4032 which has an identical 6502 board to the SuperPET. I have stripped both SuperPET's down to the 6502 board only (ie: same as a 4032), the working one continues to work, and the dead one continues to not work. I suspect ROM's, as I have seen a lot of PET ROM's go bad ... unfortunately all three machines are NOT socketed, so simple swap tests are "unfriendly". All three machines when powered on, play a little "bee-dle-bee-dle-bee" in the Pizo speaker, and clear the screen - the two working units then proceed to display "Commodore BASIC version 4.0, .... READY", while the dead one does not. Entering the command "print chr$(7)" on the dead one does NOT result in a beep, indicating that BASIC is not running (it does beep on the other two). I'm assuming that it does clear the screen, because if powered up without the CPU plugged in it displays a screen full of "garbage" - ie: the video display is "hard" and active all the time - (the CPU is one of only a few chips in a socket due to it's being "moved" to the expansion board with a ribbon cable in the full configuration). Anyone have experience with these PET's? Anyone have schematics? Suggestions, etc. welcome. Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Vintage computing equipment collector. http://www.parse.com/~ddunfield/museum/index.html