Working through some Defender CPU boards, have had decent success getting most running again, will post the repair logs later. I'm stuck on this one, board boots to ram failure error. New 4116 rams installed, voltages check out, decoder roms good, good rom board, etc.
When I run self test to test rams, it starts the test, briefly flashes Ram Failure again and then continues the rug pattern test, but doesn't report any bad ram.
I've checked the 74153s, 74ls374s and 74ls165s, as far as I can tell they are working. I have noticed that when it gets done testing, the WE line (WE3, I think) for the row of rams on bank 3 is stuck low (maybe high, I forgot, but not pulsing), while the other WE lines are pulsing. It does pulse while it is testing rams though.
Thoughts on where to look next?
Thanks in advance,
Anthony
When I run self test to test rams, it starts the test, briefly flashes Ram Failure again and then continues the rug pattern test, but doesn't report any bad ram.
I've checked the 74153s, 74ls374s and 74ls165s, as far as I can tell they are working. I have noticed that when it gets done testing, the WE line (WE3, I think) for the row of rams on bank 3 is stuck low (maybe high, I forgot, but not pulsing), while the other WE lines are pulsing. It does pulse while it is testing rams though.
Thoughts on where to look next?
Thanks in advance,
Anthony
