I recently received this Apple IIe PCB from the U.S to try my luck on salvaging the 60hz IOU and using it in my International NTSC board in the hopes of getting colour which I did successfully in my previous post. This board was advertised as untested, so that normally means “DEAD” and I assumed so.
Taking one look at the RAM suggests there were issues in the past and most likely still issues. We have some original mT ( Micron ) / Apple branded DRAMs mixed in with the various replacements. Micron don’t exactly have the best reputation in regards to reliability so this is definitely a red flag. These were used by Commodore, Atari and obviously Apple as well. I guess they were cheap!
Based on the excellent condition of the board I was happy and confident in firing it up. It displays some kind of RAM error but it’s not very helpful, definitely not as helpful as the reporting in the Enhanced IIes built in diagnostic. I don’t have a choice but to go through and check each DRAM individually.
My TopMax helps me find 4 bad DRAMs of the 8. Three of which were Micron ( expected! ).
Dead RAM chips on the left clearly marked to remind me that these are dead and not to be mixed up with working. These will come in useful for refining my Atari 8bit diagnostic tool.
I temporarily replaced the dead RAM chips with known good Micron pulls from my friends Atari 800xl. But I do have some NOS TMS 150ns chips that will be going in shortly.
Replacing the RAM confirms the fix.
It’s nice to have a second board ready to go if I need it, and the fact that it’s a non enhanced board with everything socketed is a plus. I’ll be looking at converting this over to enhanced at some point via a enhancement kit which involves a 65C02 and newer roms for Apple IIc compatibility.