Latest update:
I think the main processor has given up the ghost.
It has power and a clock input on pin 39.
RESET and HALT are high.
It outputs no E clock on pin 37.
Placing JP503 into DIAG does not produce an incrementing address bus.
The processor pins look badly oxidised so I removed it from the socket, cleaned and reseated it, but to no effect.
I think I need to find a new 6808.
Regards,Paul
