I bought an Apple IIc off ebay recently and it was advertised as having memory issues as a lot of these machines do. I ordered the ROM chip that contains the self-test code and made the necessary mods to the motherboard so I could self-test the RAM chips. When I did, it said that aux RAM chips 0, 2, 3, and 4 were bad. I've replaced all the RAM chips with sockets and tried a couple different vendors online for replacement RAM chips. No matter what I do I can't seem to get it to pass the RAM test or show different results. I've swapped chips arounds and it doesn't follow the chips. It seems to be the board itself. How can I narrow this down further? I'm confident in my soldering abilities. I've done a fair amount of it in the past. I've gone back after the fact and re-soldered chip sockets and it doesn't make any difference. I've never used an oscilloscope and I wouldn't know how to read/interpret it without someone explaining it to me.
How can I get this poor, old decreipt machine to run Aztec, Hard Hat Mack, and the original Mario Bros. once again?