Demo man Pinball ball trough errors

[imtapha]

Hi
Just picked up a demo man with a few issues,Had lost the 12 unreg supply traced fault to bridge 5, replaced to restore power.Now have message that says opto trough bad,check connections and 12v supply. I assume this relates to the ball trough,have checked the infrared leds and they are all working.The receivers check out as switching when checked with a torch.I have replaced and socketed the 339s. In switch test the optos in the ball trough do not register ie no boxes just dots. when in test1 I can get the optos to show as boxes if I short the column to the rows in the connector to the ball trough.If I do this with the machine in attract mode it goes into ball search firing the various solenoids. Anyone have any more thoughts as to whats causing the problem?

[gatordad]

check 12v test point on your power driver board again.
If you have power present
Are you sure all connectors are back in correct locations? not one pin off (ask why I ask )
Otherwise I would say you have a flaky optio transmitter on the trough board. Demo man has how many trough optio's is it 6 if I remember correctly, one for each ball plus another for the exit.
Are you seeing all 6 optio's in your switch test?

If there is a flaky optio its more likely the transmitter than a receiver in my experience. They are available to be replaced and can be fixed for pennies on the dollar vs replacing the whole board.

Just because I have run into a bunch of this lately
Any corrosion to resistor / diodes / chips/ chip legs on the cpu under the battery?

[ChadTower]

Odds are high it's a dirty opto or a cracked solder point on an opto.