CBM PET 2001 restoration tips?

Tony Duell wrote: Well I'm sort-of getting somewhere. The video signals looked happy on a 'scope, so it at least looked like it was generating *something* and so at least some basic functions were working. I pulled the display (monitor) board and was going to test that next (the schematics on the web are handy as they show the expected waveforms at various points within the display circuitry). Powered up with it supported out the back of the shell so that I could get at it, and the display sprang into life! So there's a bad joint or other connection in there somewhere, which hopefully won't be too hard to trace. The actual display's garbage, though. Perfectly readable characters - just completely random ones and filling the display. The actual characters change slightly with each power cycle, although most seem fixed. The display doesn't change with keyboard input (in other words, it seems the machine's completely hung, rather than it just being a fault in the circuitry that interfaces with screen RAM). Anyone have thoughts on that one - maybe it's a common fault with PETs? I'll have to check what the RAM organisation is on these machines - if it's x4 or x8 then I can play around with switching RAM chips around to see if it's a dead RAM chip causing the fault (if they're x1's then obviously that's not going to help me much :-) I'll check out the reset circuitry too, just in case it's that which is causing trouble... Hmmm, *probably*. I'll have to nose around the web for part numbers. It's certainly the original PCB issue (as in p/n 320008), but that's perhaps no guarantee that the ROMs are also first release. cheers Jules ps. corrected the subject line as it was driving me nuts :-) -- (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination.