I am working on a Scared Stiff pinball machine.  The issue I am having is the color DMD display is non-working.  The machine itself appears to work fine, plays a game with no issues, but just no display. 
Below is what I have tested and eliminated to be working.

1) Removed SS color DMD display and tested in a Williams Monster Bash that had a color DMD working in it.  The color DMD out of the SS machine did work in the MB machine.
Note: I am getting power to the color display as I can get the display to go to the menu while in the SS machine. Also I did update the SS color display firmware just to make sure this was not an issue.

2) Traded the two ribbon cables that go from the CPU to the AV board and the one from the AV board to the DMD display from the SS machine and tested them in the working MB machine.  All three were tried at the same time and did work the color display in the MB.

3) I did try plugging in an older working orange DMD display in the SS machine and tested.  This display did not work either.

Note: The WPC95 Audio Visual Board is a newer Rottendog board.  The CPU board has a newer updated ROM in it.
So, which board do you think is at fault?  The CPU or AV board?  Or could it be the newer updated ROM chip in the CPU board that is at fault?

Any recommendations as to what to test next and/or which board is at fault.
Thank you for your help.
Mike

Thank you for your help. I will check out what you recommended and report back.

Okay update:
1) Is there any battery corrosion at all on the CPU board?
There is none present, but the battery has been replaced with a NVRAM battery eliminator. Also the ROM chip has been replaced with a KSARCADE.NET 1.5 SS chip.
I did carefully remove all removable chips, check their legs and reinserted them. Then tested with no change.

2) I then did swap in the MB AV board into the SS. No need to swap the sound ROMs between the boards. Only will have wrong sounds, which will not hurt anything. Note: In these tests all I did was turn on the machines for testing the display to see if the display worked.
The MB AV board did no change to the SS display, but also put the AV board out of the SS into the MB and it did work the display in the MB machine.
So inclusion I would assume the AV board out of the SS is in good working condition as it did work in the MB machine.

3) If you want to try the CPU board, you only need to plug in the J210 power connector and the 2 ribbon cables at the top of the CPU board to test out the ColorDMD.
I then installed the MB CPU into the SS machine and only plugged in J210 and the two ribbon cables and tested. Machine came on with normal bong and display worked! The display did come up, but with an error message of check F106 and F101 fuses. I did check these fuses and they are in working condition. The machine did have an error message before with the original SS CPU in as the machine did dong, dong, dong after the initial one dong once its turned on (error message), just did not know what as I could not see this due to the non-working display.

Okay, the display problem appears to be with the main CPU board that has an issue, but what to check for next? Traces appear okay and have beeped them out with my meter as best I can. Also is there an second issue with the driver board with these fuses or is this just because not all connectors installed when I tested the MB CPU board in the SS machine? Not sure because the machine had this issue before I traded the SS CPU for the MB CPU.
Final note: Machine does play a game and appears to have no other problems other than some minor switches that need to be adjusted and/or replaced.

Any additional help would be appreciated.
Mike

Here are a few pictures of the SS CPU board.
No part number/revision at the top, but one on the right side.

20200910_170018 (resized).jpg

20200910_170034 (resized).jpg

20200910_170130 (resized).jpg

Great! Thank you for the information.

I did not try the SS CPU board in the MB machine yet, but can if you want me to.

Okay great, I will re-push on the socketed chips and test the SS CPU in the MB and will post an update. Might not get this done until tomorrow, but will let you know what the results are.
Thank you all for your comments.
Mike

Okay went back in the garage and tested the SS CPU board in the MB. First I pushed on all socketed chips along with U9. Normal creaking. Once turned on got the normal one dong, but no display.
I guess this determines the issue is with this board.
What's next to check?
Let me know,
Thanks
Mike

L201 is off
L202 is on
L203 is blinking
This is what the SS CPU board shows while in the MB machine.
This same thing shows on the MB CPU board while in the SS machine.
Let me know what you suggest next to do.

Okay did those reset with no changes.
Also I buzzed out tested traces between U1, U3 and J201, J202. All checked out in working condition.
What's next?

What you have said here makes sense. Unfortunately I don't own an oscilloscope, but due own a logic probe. Have not had a use for it since college and that was 1985! Anyhow I appreciate your advice and may take you up on it. Lastly I don't have the proper tool to remove U9.
At this point the issue appears to be more than what I want to tackle and I feel it maybe best for me to send the board in for repair by a professional.
Again thanks all for your help and advice.
Mike

Hi Chris,
Thanks for offering to look at this, but already sent it in to The Coin-OP Cauldron with Clive. I have used Clive for many years now and have had great success with the board repairs from him. I will keep you in mind through.
Mike

Thought I would update this with what was preformed and repaired by The Coin-OP Cauldron with Clive, the following is the results:

During the testing phase, graphics with ghosting and over-laying was observed. The NVRAM board was replaced and the problem went away. A new NVRAM has been installed (from this shop) and the old one is being returned with your board.

Work performed (all new parts):
Williams WPC-95 CPU board (no SN. Scared Stiff (revision 1.5). 3rd part NVRAM installed. No video): Game ROM removed and verified. ASIC IC at U9 removed and tested. Microprocessor removed and tested. Reflowed RAM, ROM and Microprocessor socket as well as switch header pins. Signals in, out and around board analyzed. Signals checked for geometry and timing. Busses exercised. New 74LS14 IC and 14-pin chip socket (U5). 2x zero ohm resistors (R214, R215, W3). Custom 8k NVRAM adaptor installed. J210 high temperature power input header connector. 100uf/25v/105c filter capacitor (C31). Board cleaned up. Two-tier full functional testing.

The WPC-95 CPU board has now been repaired, upgraded, fully tested and is now 100% functional. It has been installed into the Scared Stiff machine and does work as it should.