1024MAK wrote: ↑Wed May 26, 2021 10:50 am So, the resistance tests on the address lines have not shown up any short circuits or suspiciously low resistances. That points to the output stage of A11 address line being faulty.
Okay, my suggestion, if you have a known good spare Z80A, is this:
Rather than try to desolder a 40 pin chip, instead we sacrifice it....
Mark
So if I understand correctly the Z80 would be generating a very weak A11 signal.
I know it's probably a silly idea but what would happen if I pull up pin 1 and use a transistor to amplify it like in the simple composite mod? I don't even know if it would work...Surely the z80 is dying and won't last too long and I'll end up having to cut the other 39 pins....