I've been working on an Apple //e mother board for a while with no luck. It worked when I got it, and all the ICs are socketed. So I tried to use it to diagnose another malfunctioning board. Unfortunately it didn't work, and when I reseated all the original ICs it stopped working all together (no video, no beep). Finally I decided to give it a run through the dishwasher (figured that I couldn't kill a dead board) and now I get 12 horizontal bars across my screen, each 8 pixels tall. This is the most life I've gotten out of this thing in months!
So far I've replaced all the RAM on the machine, the MMU, all the ROMs (Video, EF, CD, and Keyboard), as well as the CPU. It's made no difference if the keyboard is plugged in or not, and I haven't been able to trip it into a diagnostic mode. On a lark I popped in a known bad RAM chip and got a series of As and block on the screen. I swopped out another good chip for bad and got Cs instead of As. Then I hit Control-Open Apple-Reset, and that put the Cs back to As. So I know that the computer can react to the keyboard, just not with known good RAM?
Any ideas or suggestions?