It sounds like they need to come up to check underneath - or at least that area of the board needs a very good clean to make sure there's no capacitor grot hanging around. Looks like it's been recapped (sorry, I haven't checked back in the thread), but maybe the cleaning wasn't 100% successful.
I was just chatting to IanS about this elsewhere, and he had a good idea - if you're planning to stick with 4MB, or the 4MB is soldered in, you could remove the switches, clean underneath, and hard-wire the connections.
The bottom corner pin of that right hand RAM chip definitely has some blue verdigris (corroded copper) around it, and I'd be wanting to go in there with an ESD-safe brush and 60% isopropyl (or deionised water followed by 99%) to clean up and hopefully prevent future issues.
I was just chatting to IanS about this elsewhere, and he had a good idea - if you're planning to stick with 4MB, or the 4MB is soldered in, you could remove the switches, clean underneath, and hard-wire the connections.
The bottom corner pin of that right hand RAM chip definitely has some blue verdigris (corroded copper) around it, and I'd be wanting to go in there with an ESD-safe brush and 60% isopropyl (or deionised water followed by 99%) to clean up and hopefully prevent future issues.
Statistics: Posted by philpem — Sun Feb 04, 2024 1:57 am