Thats what happened to my Apollo 1240, one day just died. I'm yet to find the problem which we think was down to battery damage slowly eating away tracks over time. The Battery was removed and replaced with coin a long time ago however some of the acid probably remained if it wasn't cleaned properly.
Does you card have any Battery leakage now or in the past?
We have re worked the components near the battery and cleaned the socket, adjusted the connector, tried another Oscilator and still no joy.
Only thing left is either track damage or CPU failure, mine never had a fan only a small heatsink so is possible mine overheated.
However the CPU's are usually soldered on these Accelerators so the biggest job is removing the old and fitting a socket.
Hope you can get it sorted, do check about the battery leakage.
Steve.
