Bad I/O Board error 52 problem from Santo Nucifora on 2013-04-10 (lisalist1)

From: Santo Nucifora <santo.nucifora_at_email.domain.hidden>
Date: Wed, 10 Apr 2013 15:55:31 -0700 (PDT)

We'll, I have spent a little while trying to fix my Lisa 2/5 I/O board and I'm coming to this list to see if anyone can help.

Here's where I am:
- The Lisa 2/5 powers up and I get a low-high-low series of beeps and an
immediate "Error 52" (COP421 error).
- There are no other options and I don't have a mouse and it's hung until I
power it off
- I can't do anything with the keyboard to stop the error

I tried "Apple S" but I don't think I'm even getting to the keyboard part of the POST
All of my cards are in it including CPU and twp memory cards
I have 3A ROM and this is displayed at the top right of the page along with the I/O icon with an X through it and the number 52

I had bad corrosion and had to redo a few traces around the battery. I also used a conductive pen to touch up some traces. I had to replace the COP421 socket because there was some corrosion around and under it. I had cleaned the board soaking it in vinegar and water. Testing continuity around it was intermittent and would only pass continuity checks when I pressed down hard on pins. I checked continuity on almost the entire board but the two Lisa 2/5 I/O board schematics I have are not 100% accurate so I've tried to use a combination of the two.

I've tried to read through the Boot ROM code but I haven't found 3A ROM source code. (I assume this is the Boot ROM for initial POST?) When I read the source, the only indication of Error 52 comes after the keyboard input is possible. Mine is happening really early and there are no clicks or options.

All traces to my COP421 are there and checked. When powered on, I cannot read the crystal output (my multimeter has a Hz mode). I can go hunting for a COP421 but I'm not sure it's the problem per se after reading much info here and other places on the net (this list is awesome). If anyone has an extra COP421 or board, for that matter, I'm all ears :)

The only other problem I have is that the capacitors on the motherboard around the parallel port have disintegrated but the motherboard still appears to be working. I figure since they are filters, it's probably okay to run and shouldn't produce this error. It was corroded as well but I cleaned it up. I have ordered replacement caps but they haven't arrived yet.. I have also not been able to find a motherboard schematic for a Lisa 2/5 motherboard other than the one at Digibarn but that doesn't really cover all components. If anyone knows where I can find a better one, I'd love a link. Everything else looks visually okay.

Has anyone else seen this or is there any other clues? Thank you for listening.

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