carlsson
Veteran Member
Today I've had a PET day. I brought out two 3032 from the basement: one known working and one labeled as "emits smoke".
Emits smoke was an understatement. The four big diodes on the power supply part of the motherboard were crackling, smell really badly and have almost corroded all the solder on the underside. However the monitor flashed a screen of garbage characters for a second before it went black.
However I wasn't sure if the major fault was with the transformer or the board, so I plugged in the faulty board in the other PET with the known good transformer/monitor. Slight crackling, then nothing happened. No display. I put back the known good motherboard, and still no action. Damn, did I break another PET by this move?
So I did what every daring hobbyist repairman would do: put the known good motherboard in the case where the bad motherboard originally came from. It can't get worse, can it? No, this time the PET powered on nicely. The monitor has a bit more burn-in than the other one but also brighter picture. The transformer is a bit cleaner wired. I had to swap keyboards though as one is very good and the other is in need for a complete overhaul.
It means I now have a PET 3032 with Basic 4 in a slightly dirty case smelling of smoke, with a monitor that shows signs of burn-in. I may try to swap parts over, but both the transformer and in particular monitor are a bit tricky to remove unless you really have to.
Ok, so what does this have to do with Frank's PET? Well, I had previously verified all his EPROMs to be OK but the last ROM (901465-23) didn't verify when read as a 2532. Therefore I swapped this ROM with my set and was greeted with a display of garbage! Back to the EPROM programmer, program a "fresh" 2532 with the same code and the PET boots again. I swapped in all the other EPROMs from his set, and my PET works OK with those except for his business keyboard layout doesn't match my graphics keyboard layout.
It means I'll send back Frank's set of EPROMs. Hopefully his PET will come alive after all.
While swapping chips, I got curious about the state of the ROM set on the board that had suffered smoke signals. It is a Basic V2 set with a PAICS ROM expansion at $B000. I put those chips into my working motherboard, and it promptly booted to the Basic V2 prompt. SYS 11*4096 also started the PAICS expansion. It suggests that even on a board where the diodes have been crackling and emitting smoke, the ROMs may still be OK. I didn't yet check the big chips: 6502, 6520 and 6522.
Emits smoke was an understatement. The four big diodes on the power supply part of the motherboard were crackling, smell really badly and have almost corroded all the solder on the underside. However the monitor flashed a screen of garbage characters for a second before it went black.
However I wasn't sure if the major fault was with the transformer or the board, so I plugged in the faulty board in the other PET with the known good transformer/monitor. Slight crackling, then nothing happened. No display. I put back the known good motherboard, and still no action. Damn, did I break another PET by this move?
So I did what every daring hobbyist repairman would do: put the known good motherboard in the case where the bad motherboard originally came from. It can't get worse, can it? No, this time the PET powered on nicely. The monitor has a bit more burn-in than the other one but also brighter picture. The transformer is a bit cleaner wired. I had to swap keyboards though as one is very good and the other is in need for a complete overhaul.
It means I now have a PET 3032 with Basic 4 in a slightly dirty case smelling of smoke, with a monitor that shows signs of burn-in. I may try to swap parts over, but both the transformer and in particular monitor are a bit tricky to remove unless you really have to.
Ok, so what does this have to do with Frank's PET? Well, I had previously verified all his EPROMs to be OK but the last ROM (901465-23) didn't verify when read as a 2532. Therefore I swapped this ROM with my set and was greeted with a display of garbage! Back to the EPROM programmer, program a "fresh" 2532 with the same code and the PET boots again. I swapped in all the other EPROMs from his set, and my PET works OK with those except for his business keyboard layout doesn't match my graphics keyboard layout.
It means I'll send back Frank's set of EPROMs. Hopefully his PET will come alive after all.
While swapping chips, I got curious about the state of the ROM set on the board that had suffered smoke signals. It is a Basic V2 set with a PAICS ROM expansion at $B000. I put those chips into my working motherboard, and it promptly booted to the Basic V2 prompt. SYS 11*4096 also started the PAICS expansion. It suggests that even on a board where the diodes have been crackling and emitting smoke, the ROMs may still be OK. I didn't yet check the big chips: 6502, 6520 and 6522.