trough jam opto getting killed *FIXED*

[lilshawn]

I have a stern pinball indiana jones (newer) that seems to keep blowing the transistors on the trough jam position optical switch.

I swapped the board out of a working unit...worked okay for a few hours and now its blown again. Thr reciever led is good, emitting about 1.2 volts when the transmit LED is shining on it and less than .2 when blocked.

Seems the transistor or the FET on the board is getting shorted out, either by voltage getting backfed through the switch line or something else.

I don't think it's a logic problem, as the board doesn't work once replaced in the doner machine.

The first position opto still operates normally.

Anybody have any ideas or have experienced a similar issue?

[lilshawn]

replaced the board and was still getting an intermittent switch.

seems a bad wire on the board plug (Insulation displacement type) had a bad connection.

the intermittent connection seems to stress out the transistor/FET causing it to blow.

Visually the connector looked fine but probing with a logic probe showed that the signal was getting generated but not being received.