Hello, a little while ago I was given a 2001 series Commodore PET. It seems to not work, but I think it is repairable. I am not versed in hardware, but would like to get the PET working in order to showcase the history of computing in my classroom. After a little research, I found out that it uses the 6502 microprocessor and found my way here. Apologies if this is in the wrong place, but perhaps someone here can point me in the right direction.

http://www.youtube.com/watch?v=n1eB4KGn03Q

The last 10 seconds demonstrate the garbage that gets displayed when I turn the computer on, off, and then on again.

Also note that there is a blue wire that goes to a capacitor just next to the 6502 microprocessor (on a 'groove' labeled F), and connects to a button on the side of the monitor. One of the blue wires is not connected to anything. I (think I) do not see this present in online schematics.

Any information I could use as a starting point would be great, since that is about all I know at the moment.

Hi, no problem here surely is a forum to ask for some 6502 hardware debugging help, although here it is more general.

You might want to have a look at the VCF Forums:
http://www.vintage-computer.com/vcforum ... -Commodore
or ask the CBM hackers mailing list http://www.paradroid.net/cbm-hackers.html
Some general PET information actually is on my PETindex site: http://www.6502.org/users/andre/petindex (links to schematics under "boards").

Now, looking at your coutube video...:

First I think the blue cable that goes to the push button under the monitor looks as if someone added a reset switch - which the original PET lacks. One of the blue wires would go to ground, the other to the CPU's RESET line. The capacitor is to avoid signal bouncing.

The garbage on the screen shows that at least a lot of the system seems to work, namely the power supply, timing, video generation logic (this old PET has the video timing hardwired) and even the screen. Is this garbage screen constant? Or are the characters changing over time?

There is one thing that these PET are known for - you can try to take the socketed ICs out of the sockets one by one and reseat them. The PETs are known for the chips coming loose and reseating helps here.

If that does not work, to check what is broken you would need to do some measurements on the signal lines. I don't know how much you know about electronics and how much experience you have. Maybe it's better to ask someone on the VCF Forum or the cbm hackers list who lives close to your place to have a look.

André