Switch power is going low for some reason. Color Display or DMD.

Something else going on.

LTG : )

Sounds like a classic power supply issue.
None of my ColorDMD displays ever blackout.
I'm guessing you're loosing 12VDC but could be the 5VDC going low.
Have you rebuilt the powersupply / rectifiers?

Theirs a little cap for the 12vdc on the driver board . It often leaks and eats through a trace causing issues. Since you're losing display and optos I would check this area.

There are two +12VDC supplies on the power board. They should not be confused because they serve different purposes. They originate from different transformer secondary windings.

+12VU: UNREGULATED +12VDC. This is derived from its own transformer secondary winding at J112. It connects to the DMC (dot matrix controller) and is a pass through to the DMD (dot matrix display). Certain brands of DMD require the +12VDC input. It is NOT used by DMC. I believe ColorDMD requires this +12VDC.

+12VR: REGULATED +12VDC. This is derived from the +18VU lamp matrix transformer secondary winding at J101. It is regulated by Q2 and C2. C2 does leak and when it does it can cause problems to the nearby traces as well as interfere with the +12VR supply.

+12VU supplies the playfield. Anything that needs +12VDC in the playfield uses this power source. This is includes the opto boards and the opto board LM339 ICs.

+12VR is only used by the CPU/FLP boards - exclusively for the switch matrix LM339 ICs.

DumbAss stated this perfectly, I have nothing to add.

Edit: okay I do have one thing to add. In case you are unaware DumbAss actually builds the WPC089 board set, and while I do consider myself an expert with this specific board set, he may actually have more specific knowledge in this area than I do.

Another thing I would trouble shoot is the mpu board. I am not sure on testing it but I know how to swap and pop. Lol

I Had a similar experience on my Addams family and it ended up being my mpu. If you have a spare or another game you could borrow one from, try swapping it out and see if that fixes it.

I am sure another member or DumbAss (lol) might be able to help you on actually testing the mpu.

Oh make sure its the same type of mpu you are swapping, I believe its a mpu089.

This is an excellent strategy. I use it all the time. It's part of the reason for me building my own boards. It's always useful to have a known good board for differential diagnosis or to use an emergency replacement.

Based on the collection list OP cannot swap the CPU boards between STTNG and WCS94. OP can however swap the PWR boards if OP suspects a potential problem on that board.

agreed, I also keep a full set of WPC089 boards available for comparison testing.

Coils like the trough eject will fire when the 12V (unregulated) power to the playfield is unplugged. The optos aren't getting power and will be detected by the switch matrix as a ball obstructing light from the opto (i.e. switch closed). The coil will fire in order to eject the phantom ball.

This is one of the three harnesses plugged into J116-J118 at the lower left corner of the board. One goes to the backbox (DMD controller board), one goes to the playfield (optos/motors), and one goes to the cabinet (coin door).

If you have the ColorDMD harness plugged in, whatever cable was unplugged from J116-J118 needs to be plugged back into the center connector on the ColorDMD harness using the male-to-male "z" adapter. Make sure the wire colors match on both sides of the adapter.