General Category > Lisa Troubleshooting and Repair
Lisa Video, ProFile power issue, NiCad Leak fixes, etc.
rayarachelian:
--- Quote --- The 6504 does get pretty hot, so maybe something is wrong with it.
--- End quote ---
That doesn't sound good at all. :( Hope your replacements arrive soon.
AlexTheCat123:
--- Quote ---Hope your replacements arrive soon.
--- End quote ---
I hope so too! The only place that I could find a replacement 6504 was in China, so it could take around two weeks to get here. The 2732 ROM will arrive on Wednesday or Thursday, though. I'll keep you posted about the results of installing the new parts!
rayarachelian:
Yeah, it could have gone bad, but, any chance there's a short somewhere on the 6504's socket, or an output being sent to something that only the 6504 itself should output like address lines?
If you pull out the 6504 and put it on a breadboard and give it +5V and GND, does it also heat up? I'd worry about these before replacing the 6504 with another - if something on the I/O board is causing it to fry, it will damage the replacement too.
Sadly, yeah, 6504s are rare. They're just 6502s with extra I/O lines, but ofc you can't easily replace them with a 6502.
patrick:
6502 and 6504 are based on the same die, they just have different packages. So you could use a 6502 with an adapter socket. Connect A12..15 low and /SO high. Certainly you don't want piggiback boards in a vintage machine, but for a quick check this should be acceptable.
Have you checked the reset signal on the CPU board? Sometimes capacitor C8 gets leaky and the NE556 will stick low. To confirm this, you could disconnect C8 and use the manual reset button on the back of the machine.
For the COP421 I have designed a replacement board a few years ago: http://john.ccac.rwth-aachen.de:8000/patrick/COPSreader.htm. This was intended as a tool for software analysis, but could also be used as a replacement for a defective part.
AlexTheCat123:
--- Quote ---Yeah, it could have gone bad, but, any chance there's a short somewhere on the 6504's socket, or an output being sent to something that only the 6504 itself should output like address lines?
--- End quote ---
I've checked the socket and there aren't any shorts or any signals going places that they shouldn't.
--- Quote ---If you pull out the 6504 and put it on a breadboard and give it +5V and GND, does it also heat up?
--- End quote ---
Yep. It still heats up on the breadboard.
--- Quote ---Have you checked the reset signal on the CPU board?
--- End quote ---
The reset signal looks good. It goes low for around a second to reset the 6504 and then it goes high again.
--- Quote ---For the COP421 I have designed a replacement board a few years ago
--- End quote ---
I made one of your COP421 replacement boards a few days ago and I have it installed in my Lisa right now. I think I accidentally called it the X/COPS in a few previous posts because I was browsing eBay and saw one that seems to be made by VintageMicros that's called X/COPS and I just got the names mixed up. It doesn't seem to be relaying signals from the keyboard and mouse to the VIA, but it's definitely sending signals to the LS153 mux that connects to the keyboard and mouse and it's sending sync pulses to the keyboard as it should. I'm guessing that this is related to the I/O board error 57 that I'm getting and that it will start sending these signals to the VIA once the Lisa can pass the self-test without any errors.
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