I have an EPS that I have verified (without doubt) it has a Main PCB fault.
I have swapped the PSU, Keybed and display into a working EPS and they all work as they should. I have determined that the Uart and the 68440 IC are not seeing any CS signal. I am not sure where to go with this from here. Does anyone have any input? Or perhaps there is someone on this page that can fix the main PCB for me if i send ti to them? THAXN Don Voth
You’re at a dead end I’m afraid. I have a similar story and after consultation with Dr Buchty, he explained that just like in the ESQ1/SQ80, the DOC chip is kind of in charge and coordinates the other chips, ie CPU, DUART etc. The trouble is that the EPS uses the even rarer DOC2 which was only used on the EPS and some uncommon high end PC soundcards in the 90s. By all means try the other stuff especially the stuff that is socketed. Keep that machine for spares and get another one.