As you know I had no luck reviving the AlphaServer 4100 after it blacked out on me when I initially powered it on. Having traced the issue to the PCI back-plane subsystem via a lot of LED chasing I hunted down some replacement parts. As luck would have it a guy was selling a load of DEC gear on eBay including parts for a 4100. I managed to obtain a MC bus to PCI backplane adapter board (where the fault reading LEDs are), PCI backplane board (which I suspect is the faulty part and is preventing the PCI subsystem coming up), front panel (the original is broken and although it works the reset button doesn’t work that well) and the RIO comms board that sits in the bottom of the PCI bay and carries the serial ports.
My thinking is that the PCI bay was the most exposed part of the machine while it was in storage and looked like it had been subject to damp. I suspect therefore something failed on the PCI backplane when I booted the machine up and left it running for a few minutes because it had been damaged by the storage conditions. Replacing the RIO board is a precaution I decided to take after bartering a reasonable price for one with the seller as it’s in the bottom of the same bay and may well also be damaged. Even if it’s not I want a spare in case I blow it up trying to find a 12V power adapter that works in the plug on the back.
All I have to do now it methodically replace each part in turn and see if it gets us anywhere. Fingers crossed, eh?