I've been having difficulties with my old Apple ][+ and got some excellent advice from https://www.applefritter.com/comment/96037#comment-96037.
Even after replacing all the caps in my PSU, my monitor would show random green squares. Many have suspected a faulty RAM chip (or multiple faulty chips), so I reseated all the chips and still had the problem. Next I pulled out all the RAM except for the row closest to the keyboard. Since I still had the problem, I replaced that row of RAM with the chips that were previously the second row... and it worked! I plugged the floppy card back in and that worked, too!
Next, I plugged previous row 3 into row 2 and it still worked. Finally I plugged the original row 1 into row 3 and had a problem. So, there's a bad chip in the original row 1.
When reseating, I noticed that many of the pins looked corrupted. So, perhaps not wisely, I tried to filing off the corrosion with a fine emory board. I was able to do 5 or 6 with not problem, producing a result like this:
I must have been a little too confident, or perhaps I got a too aggressive with the filing, or perhaps one of the pins was just too corroded, but I now have a couple chips that look like this:
Great. So now I need some replacement RAM. The chips say TMS4116-20NL, however, underneath I read AP8114. Others have AP8118. Does it matter what's underneath? I found https://www.questcomp.com/part/4/tms4116-20nl/408290989 so I'm wondering if I should just grab a half-dozen of those. Or maybe I should grab 24 and replace them all. Any recommendations? Thank you!