Quoted from arolden:Hi all.
I need some help with diagnosing a lamp issue on JD. All lamps on column 4 are not working. All of these lamps are on the large lamp board in the bottom centre of the playfield. I have checked all of the bulbs are actually working - they are. I have checked all of the diodes and solder joints on the lamp board - all good. Solid 18v is present at TP8. I have checked for continuity from J137-4 in the backbox to each of the lamps - all good. I have also checked the transistor at Q95, which controls this column - all good. I also did the jumpered lamp socket test (between J133 and J137), and all columns lit the test lamp properly.
I'm not sure where to go with the troubleshooting from here. I suspect that I need to start looking at the ICs on the power driver board, but I do not have a logic probe.
Thanks for any help.
Check the connectors again, check the connector pins of the lamp board.
Also reseat the ribbon cable from the CPU to the driver board on both sides.
How did you test the TIP107?