Well, going to start from the beginning because the DMD not displaying is the last issue that has happened.

After playing ST:TNG for about 3 hours the left and right inlane eddy sensors started functioning intermittently, after another hour they stopped working completely. This had been happening on the machine since I got it, but it didn't happen all the time so I just let it go. After 6 hours the sound cut completely out and I turned it off for the night. The following morning I booted it back up and the sound worked just fine, I pulled out and examined the sound board and it looks just great.

A couple of days later I booted it up again and nothing displays on the DMD, I am using a color DMD which is receiving power just fine from the power driver board. At this point the LED on the DMD controller board was lightly flickering every few seconds. The machine boots, you can start a game and all solenoids/lights/sound are functioning normally.

And here is where it gets weird. I swapped out the dot matrix controller board for a board that I know 100% works and the machine wouldn't fully boot. Same flickering every few seconds but no display and you are not able to start a game and play, I also tried a brand new rottendog board that I was going to put in my AF restoration, this displayed artifacting on the DMD display but the game never fully booted. The first board allows the game to boot, others just leave it hanging.

What I have tried:

1. Reseating all ribbon/pin connectors
2. Examining/voltage testing 2 power driver boards (perfect)
3. Swapping ribbon connectors from another machine
4. Swapping DMD controller boards 2x

And I'm stumped! At this point I'm not even sure what would cause what is happening, any guidance would be greatly appreciated. Thanks for your time!

Thanks for the suggestions, I will have some time to work on it this sunday, will keep this thread updated when I have more info!

No Khar boards on the machine and no prior reset issues. To clarify it has never reset during play, it is just failing to boot or booting with no display on the DMD. Thanks for your time, looking forward to diving back in on sunday

Alright, had a good chunk of time to troubleshoot last night and gather some information. Thanks everyone for your suggestions, here is what I have done with some pictures for reference.

Coming back to it this sunday the machine would not boot at all, D19 and D21 remained lit but no sound, lights or solenoids w/ no display on the DMD.

First, I reseatted the U6 ASICC onto a new board. Sound board dongs every 10ish seconds, this also produced a flickering of the LED on the DMD controller board and some snowy static on the DMD. D19 and D21 are lit consistently on the CPU. While testing voltages on the power driver board some lights flickered and a few solenoids fired, while this was happening D20 on the CPU and LED3 would flash while the lights were flickering.

I should also note that some fuses blew during this time while the lights were flickering, F104, F105, F106 as well as F114. In addition the 8A slow blow in the transistor box.

Test Voltages for Power Driver Board:

TP1 - 13.49
TP2 - 5.09
TP3 - 11.84
TP4 - .3
TP6 - 70.3
TP7 - 21.3
TP8 - 17.7

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After this I swapped back in the old CPU, the D10 LED on the DMD controller board flickers intermittently and the DMD is blank, no flashing of lights or solenoids firing. D19 and D21 on the CPU remain lit with no flickering of D20, sound board does not dong. No blown fuses. I tested voltages again for redundancy. LED 3 on the power driver board is also staying on when powered with the old board.

Test Voltages on power driver with old CPU installed:

TP1 - 13.6
TP2 - 5.06
TP3 - 11.75
TP4 - .42
TP6 - 70.3
TP7 - 21.3
TP8 - 21.5

Still at a loss as to why the machine will not boot up, however learned quite a few things in the process so I guess that is a positive. Any help where to start next would be greatly appreciated. Thanks for your time and consideration.

I believe I have narrowed it down, I started by plugging everything in and then removing 1 ribbon cable connection at a time. After disconnecting J601 on the dot matrix control board the machine booted.

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After this I tried another ribbon cable and then replaced that board with a proven DMD controller board with the same results. the J601 connects to the sound board here and it looks pretty rough.

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Is it possible that the damage there is causing information not to get to the DMD controller board? I think this would explain the sound dying shortly before these issues started. Thanks again for the help, much appreciated!