I'm trying to troubleshoot a Stern MPU-100. The LED is locked on and most of voltages check out, but the TP6 measures .2vdc.

My fully working Bally -35 has a TP6 that measures 11.70vdc. I can't find much info on what it should measure. Should I care about this? Could this be a symptom of the problem or should I focus on the other more common culprits?

It does have minimal acid damage. All the traces check out though. Pin 40 is high, 5vdc.

Acid damage was cleaned and suspect components were desoldered, tested and re-installed (just a few were affected). New 5101 chip installed using sockets (all traces check out).

I noticed that the new ROMs installed are cooking! You can't touch them - doesn't seem right. I modified the board to use two 2732s per clays guide. I do not know if the board worked previously or not since I did not have any ROMs for it.

Maybe these will help?

Stern_MPU_002_(resized).JPG

Stern_MPU_003_(resized).JPG

Stern_MPU_004_(resized).JPG

Stern_MPU_005_(resized).JPG

Stern_MPU_006_(resized).JPG

Stern_MPU_007_(resized).JPG

Stern_MPU_009_(resized).JPG

Well that helped - thanks! They were upside down (not sure why the labels are upside down when installed correctly?).

Unfortunately not much has changed - LED still locked on.

Definitely my bad. I know better and just didn't pay attention when I installed them. Thanks for the help. I still think the board is worth trying to save so I will order a couple more and pay better attention this time. Lesson learned.