PM sent
I have come across one other machine that has had the bell opto fail twice. I inspected it after the first one failed but i only installed the second replacement board and spent a couple of hours (which i only charged my fuel cost and had other repairs to do there any way so i didn't actually charge for the opto fault) And could not find a short or possible short anywhere. The part on the opto board that failed was the FET on the board that the opto controls and not the actual opto receiver or transmitter leds.
The fet is a 20 volt 2.5 amp device but it has a resistor on the gate and the source and both resistors are only rated at 100mw or less and are fine.
There is also a 100mw diode which is on either the source or drain which has not failed yet the FET has gone short.
That was for the electronics people.
I have my 'theory' on this and it involves transients across the gate source junction because for anything to drain more than 2.5 amps through the circuit to kill the Fet it would destroy one of the resistors let alone the very thin tracks on the board.
The opto board has not failed again after many games
