Williams Gorgar (Williams, 1971) Machine random reset

[malusj18]

I have a Williams Gorgar machine. When the right flipper is it hit randomly resets. Could be one hit or could not happen at all during play. The issue seems worse when machine warms up. We have changed connector pins, checked flipper diode, and checked power supply voltage with connectors hooked up and not hooked up. The only issue we have found is that we have 12 volts on the power supply board until the connector is hooked up and then it drops to eight volts. Are there any suggestions on what the problem could be?

 

[pinballdaveh]

power supply 12v problem. both the 5v and 12v get power from f5. before that fuse is c15 filter cap , d7 and d8 diodes. if c15 has a cold solder connection, bubbling or defective ac ripple will pass thru both 5v and 12v circuits causing problems on cpu board. checking or changing c15 on power supply board would be a good start.