Help restoring a Mac Classic M0420: sad picture 00000001/0000FFFF

[billbucks]

Hello,
I'm trying to fix an old M0420 Mac Classic. When I start the Mac, I get a sad picture:
0000001
0000FFFF

I found the following page: https://tinkerdifferent.com/resources/sad-mac-error-codes.82/
Based on this information, 00000001 mean the ROM test failed and the sub code is meaningless.

Is it something that can be fixed with a a software or hardware solution ? I have a spare motherboard from a Mac SE ; could it used to swap the chip ?

Thanks
Bill

 

[retrotechtive]

Have you tried a bit of Deoxit in the socket, or reseating the ROM? It the only thing that is normally in a socket on the Mac Classic board.

Failing that, the ROM image does exist on the web, and could be burned to a chip like this:

https://retrorewind.ca/27c400

if you have a way to get the image onto it. Retro Rewind might be able to do that for you if you contact them with a valid ROM image (and proof you have an original).

 

[retrotechtive]

Something else I should add: have you inspected the logic board at all? On both of the Classic machines I've worked on, the capacitors were leaking quite badly and needed to be replaced. Definitely worth checking if the board has been recapped at all, and if not, getting that done to preserve the board. It could in theory even cause issues like the one you're seeing.

 

[billbucks]

Thank you for the suggestions .
I'm going to start looking at the board.