ClassicHasClass wrote:Dude! Which PET?
I actually picked up three of them for free about a month ago... and ironically managed to give away the most easily fixed one, which was a chiclet-keyboard 2001-8. (But oddly, it has a PET Dynamic motherboard in it. I don't know if that's stock/correct for a really late 2001 or if it was repaired with a later board.) I still have a 9-inch screen 4032 and a CBM 8032, and both need a lot of TLC. I've been concentrating on the 4032 mostly because its monitor works. (TTL scares me less than CRT problems.)
The poor 4032's a wreck. So far I've fixed two broken traces which were preventing both system RAM and VRAM from being written to. (There's still some screen corruption that I hope is just a bad 2114.) At this point it will crash to a ML monitor screen with no keyboard activity, which is a vast improvement from where it was, but I'm worried there's a long way to go. (Best guess at the moment is there's something wrong with the 60hz interrupt.) In the process of working on this I've actually taught myself enough 6502 assembly language to write a primitive diagnostic EPROM that fits in place of the F000 Kernal. It's pretty crude, all it does is flip-flop between doing a really elementary test of the first 1000 bytes of RAM and displaying the full character set on the screen in an endless loop with a two-second-ish delay between cycles, but in my defense it's really hard to do useful work when you're restricting yourself to *only* running from CPU registers. (You get three 8 bit ones, if you can't trust RAM for a stack at all you can't do any subroutine calls, and it's also a *huge* pain to not be able to use the zero page. I guess that's what makes it fun.) It did work to provide enough useful bus activity for the logic analyzer to find some problems, at least.
But... yeah, loads of fun, considering I'm almost a complete newbie in dealing with electronics outside of Radio Shack discovery kits.
I also picked up three PET disk drives. (A 2040 upgraded to a DOS 2.0 4040, an 8050, and an MSD SD 1. Two out of three pass diagnostics, the 2040 claims it has a bad ROM.) I hope someday to actually have a machine to use them on. :^b