Hey y'all,
I got an IBM PC a while back that doesn't POST. I recently got a probe to check, and it seems like the RAS and CAS don't strobe at all.
The chips behind it on the schematics seem to be fine, with the RAS and CAS S138s receiving strobing on 2 of the 3 input lines, and strobing on the control lines. I doubt that two S138s would fail, and the control chip for the RAS failing wouldn't explain why the CAS doesn't strobe either.
I'd buy diagnostic ROMs but the only person who's selling them wants around 50 bucks shipped. If anyone has a source for those Landmark ROMs that isn't too expensive please send it to me, I can't find any.
What would be the best way to fix this?
Thanks,
Zhinü
View attachment 1238181
I got an IBM PC a while back that doesn't POST. I recently got a probe to check, and it seems like the RAS and CAS don't strobe at all.
The chips behind it on the schematics seem to be fine, with the RAS and CAS S138s receiving strobing on 2 of the 3 input lines, and strobing on the control lines. I doubt that two S138s would fail, and the control chip for the RAS failing wouldn't explain why the CAS doesn't strobe either.
I'd buy diagnostic ROMs but the only person who's selling them wants around 50 bucks shipped. If anyone has a source for those Landmark ROMs that isn't too expensive please send it to me, I can't find any.
What would be the best way to fix this?
Thanks,
Zhinü
View attachment 1238181