I am trying to fix an Apple II europlus.
It can't boot and it looks to be related to a ram problem. Or maybe that's just a red herring.
If there is a ram chip in C3 or D5 or E3 it displays a weird screen. See picture 1 and 2.
If there is NO ram chip in C3 and D5 and E3 it displays a more normal screen. See picture 3. But of course then it can't boot without the C3 ram.
I have tried using ram chips which I have tested ok in another machine.
I have tested all the 74LS chips on the board, they seem to be ok.
I have tested the 6502 and the roms in another machine, they work ok.
I tried desoldering the C3 socket, because maybe there was a problem with the socket. Did not find any problem there other than destroying the socket. I put in a new socket, that did no change the behaviour.
Any ideas as to what the problem could be? Where I should be looking?