[~rf~]

I opened up the 888/24 I/O interface that failed first. Did some troubleshooting and when I disconnect the output ribbon cable, it powers up.
Is it possible that something has failed in the output circuit?
Does the power supply have a circuit for the output bus?

I have another older 888 16 bit that has the same symptoms. I can really hear the clicks coming from something somewhere either on the main board or the power supply.
Does anyone know what has failed and if this part is easily replaced/repaired?
Is there a schematic available for these older outdated interfaces?

Thanks