DeChief
Member
So I recently purchased a busted Commodore PET here in Japan and I've been trying to revive it, but a lot of the information out there is conflicting and/or doesn't apply to my PET's motherboard.
It has what seems to be a common problem: garbage on the screen upon boot. It goes past that to a black screen almost immediately afterwards and it looks like the monitor is off completely, although I can hear that it is still on. Sometimes when I plug it in it goes to a screen where I can see the cursor flashing, but there's a bunch of misplaced characters everywhere that change and multiply whenever I type something. Pressing shift+clr clears the screen to a flashing cursor up the top left. I've only been able to get it to boot like this a few times and I can't think of a reason why it would alternate between doing that and just going to/past the garbage screen. It's probably relevant to mention that the switch on the back appears to be locked in place somehow, so the only way I can turn it on and off is directly via the wall plug. Judging by the label on the front of the machine (in Japanese) I think it might've been a computer that stayed on for long periods of time. That would also explain the individual heatsinks present on four of the chips.
So far I have:
- cleaned the board thoroughly - nothing changed
- removed the two 6520's and tried booting it - nothing changed
I can see that some of the pins on the smaller chips on the bottom right corner of the board have what look like rusty pins (sort of black-ish brown), but I checked the continuity on them and they appear to be alright. Before I go spending any money and replacing things, could somebody try explaining to me why nothing happens after the "garbage screen"? I don't want to replace any of the memory chips because the screen displays both english characters/numbers and Japanese katakana characters, which would make sense considering that the keyboard also has katakana on it (along with english).
I'd really like to save this machine, so any and all help would be appreciated.
Thanks!
It has what seems to be a common problem: garbage on the screen upon boot. It goes past that to a black screen almost immediately afterwards and it looks like the monitor is off completely, although I can hear that it is still on. Sometimes when I plug it in it goes to a screen where I can see the cursor flashing, but there's a bunch of misplaced characters everywhere that change and multiply whenever I type something. Pressing shift+clr clears the screen to a flashing cursor up the top left. I've only been able to get it to boot like this a few times and I can't think of a reason why it would alternate between doing that and just going to/past the garbage screen. It's probably relevant to mention that the switch on the back appears to be locked in place somehow, so the only way I can turn it on and off is directly via the wall plug. Judging by the label on the front of the machine (in Japanese) I think it might've been a computer that stayed on for long periods of time. That would also explain the individual heatsinks present on four of the chips.
So far I have:
- cleaned the board thoroughly - nothing changed
- removed the two 6520's and tried booting it - nothing changed
I can see that some of the pins on the smaller chips on the bottom right corner of the board have what look like rusty pins (sort of black-ish brown), but I checked the continuity on them and they appear to be alright. Before I go spending any money and replacing things, could somebody try explaining to me why nothing happens after the "garbage screen"? I don't want to replace any of the memory chips because the screen displays both english characters/numbers and Japanese katakana characters, which would make sense considering that the keyboard also has katakana on it (along with english).
I'd really like to save this machine, so any and all help would be appreciated.
Thanks!
