This is a continuation of what I talked about on the other repair thread you had opened. People lose the history on the game.

If your any of your high voltages (-112. -100, 62v) failed, you really should rebuild the whole high voltage section.

I urge you to go back to the seller and see if he would swap out the board for a working board. Never know unless you ask.

It's fairly straight forward actually.

DMD Connector (resized).jpg

Dot Matrix Controller J604 (resized).jpg

Dot Matrix J604 Schematic (resized).jpg

People who restore and sell games usually like helping out, especially when something goes wrong so quickly after pickup. Just mention it to the seller and ask if you can buy/trade for another working DMD controller board from him.

As many games as I have bought over the years, people are willing to help in some form or fashion. There is just no way to predict everything that can go wrong within a 1 year period with a game you are looking over in a short time period when buying a game. Knowing the seller had rebuilt the high voltage would have even been enough for me to not worry about looking over that board.

The high voltages for the DMD are generated on this DMD controller board. Sometimes a DMD can take out a DMD controller and vice versa. Sounds like this has happened.

http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Testing_DMD_Controller_Power

These are the parts that go into a full high voltage DMD controller rebuild.
https://www.greatplainselectronics.com/proddetail.asp?prod=WPC-HVP-KIT

I believe there is a diode on the bottom left area of the DMD controller board that may be shorted. That should be something you can measure resistance (ohms) with the power off on the game. 2019-10-22 13_45_01-Dr Who dead display - help _ Tech_ Modern games _ Pinside.com - Internet Explore (resized).png

Diodes would normally short so you would see zero ohms. If you use the diode test, you should see 0 volts across them. If a diode opened, I would expect you would see the diode physically damaged.

There are several diodes in that area so test them all. I just do not have the schematics available today or tonight to look at. It is a quick test, so should be easy enough to test them all.

Yes. That is why I hope you find a shorted diode on the 12v line. If you have the schematic available you could test the exact diode that goes to J604 pin 7 that is shown in the partial schematic in post 5.

Compare the resistance of the T2 DMD and the DR WHO DMD. Disconnect the cables from both. Measure the resistance between pin 7(+12) and pin 4 (GND). Most likely the DR WHO DMD will measure a very low resistance. Maybe 1 or 2 ohms?

Measure the resistance on the DR WHO one then.

Well, I just looked at the schematics. There seems to be 3 different versions of DMDs. Only 1 of them uses the +12V.
There are 2 Babcocks. One of them uses the +12V and the other does not.
You(according to your pics) have the Cherry DMD which according to the schematic does not use the +12V. Of course there probably is a version which does use the +12V but these are the only schematics I have. Again, measure the resistance between pin 7 and 4 on the DMD with no cables connected. If you have the DMD that does not use the +12V then the resistance should be infinite ohms. Basically no connection. I don't know what else to suggest. Did you replace the ribbon cable? You sure it's installed correctly? Maybe you should just buy the Color LED display.

DMD Cherry (resized).jpg

With power off, try pressing on the U9 ASIC chip on the MPU board.

It I best not to press on parts while game is on, same with reseating cables.

Try pressing the other socketed parts on the MPU and reseat this ribbon cable.

Ribbon cable reseating 4 connector (resized).jpg

I think you are on the right track... Symptoms all point to a faulty ribbon cable. Also, from my experience, it's the most common failure on this era of game.

Replace cables, re flow solder points.