I just diagnosed a similar issue on a large Sega DMD, can't remember if yours will also have it, but look for an unhooked ground strap that goes on a corner screw down

On the DMD driver board

Well your not alone with this issue, you probably already checked but could the 14 pin ribbon be plugged in upside down? Verify that the red stripe is on pin 1 on both connectors

When the dmd went out on my DE JP, I traced it down to a bad 3 pin connector for the 5v.

Possible, it could be a board issue too

Iirc , when you buy colordmd ROMs , you also get the eproms? , If so do you still have the old ones?

ColorDMDs are downloaded via a thumb drive from the website. They rely on the original eproms to work. It simply "colors" the code.

Interesting to see how this turns out.
You should still get the code version displayed before it goes blank if the MPU is not sending signals.

One of two things, really, I know you've replaced boards, but let's step back, I'm order for the DMD to display it needs communication from the driver board,

The board has been replaced, in order for it to relay the to the DMD, it needs a stable and solid 5v, have you done the service bulletin 106 ? If so you should read 5.03 v with dmm, I

If you are getting 5v at the controller board (red pin 1, black pin 3) then

The controller has the 20 pin from mpu to driver board and 14pin from driver to display,

Since you have verified correct orientation and swapped with known 14pin, look at the 20pin, test the Simpsons ribbon cable,

If that doesn't work, look at your grounds, is it connected? Is it corroded? Damaged?

If all the above checks out, then test mpu theory using a know good mpu , if it works the board has an chip issue

If it still doesn't, look at the 5v line again

I pulled the MPU to DMD cable on my JP lost world to see what happens. Even without connection to the MPU, it still shows the name of the game before going blank.
If you're getting nothing, I'm guessing small cable or 5v power to the driver board.

Exactly!

Can you post some pics of your set up? The back of the colorDMD, the driver, power supply board. I want a visual look at everything.
BTW, I'm dealing with the same issue on a large DMD Frankenstein. Have mine narrowed down to the 14 pin cable or grounding issue.

Have you tried flipping just one end of the 14 pin cable, not both ends?
It wont hurt anything.

My previous reply stated a solid 5V absolutely nothing less. Board is very temperamental. Look up service bulletin number 106 follow the instructions, this is likely to fix your problem. Also, make sure to ground the board at screw down, connect it's ground to main ground strap. If you can't complete the circuit it won't work. It need power and ground. Let us what happened.

Bulletin 106 is only for jumbo DMD games. This is a regular size.

I would get a ground strap/wire to that J7 hole on the new driver board.
Another thought, is that ROM chip seated correctly, no feet bent under,? I've done this before.

I have done it too lol, are the ROMs seated with the notch pointed up?

Brain fart, service #106 is for large DMD

But , that stable 5v is a must

It appears the holes have metal eyelets in them for grounding on the metal mounting screws. There wont be any traces, that's a giant ground loop around the outside of the board.

This!

Thought maybe your +5 and ground were backwards on the dmd driver board, but doesn't appear to be the case.

Try putting a ground between the metal post ant the back off the board where it screws

It means when the board is mounted on the metal bolts that hold the DMD in, the board is then grounded to the machine. The metal eyelets in the mounting holes touch the metal bolts creating a common ground.
You have it mounted on plastic pins, therefore the board itself really has no ground to the rest of the machine.

I'm also suspect of that slightly low 5v power.

This happened to me last night lol

Seriously look do those 2 things

IMG_20190721_015034 (resized).jpg

Yes, my test rig has a separate power supply for the florescent lights though so I just ran from the 5v off it

As someone suggested inspect your connector on the driver board, too

That's supposed to be in tolerance, but boards are finicky

The 4.8 when on is suspect!

I worked on enough of the DE 128x32 DMD games to say 4.8v at the DMD controller board is ok as well as 4.94v on the power supply. Even with that said, at some point, I suggest all the electrolytic capacitors be replaced as they tend to fail after this long period. Caution is needed to remove them as they are difficult to remove.

Is the game booting up? You can see the left 2 red LEDs are lit on the MPU? Game is in attract mode with the controlled insert lamps cycling?

If not, test these 2 fuses to be sure they are not blown.
20161122_213122 (resized).jpg

Can you count the flashes? Looks like your MPU has an error. It should repeat after a pause.

Post pictures of both MPU boards. There is a jumper change needed if going from a single EPROM to 2 and vice versa.

MPU board, as that is where the boot up issue is. Simpsons MPU uses 2 game EPROMs and SW uses 1 game EPROM. Junper must be set properly for each game.

You need to change the jumper on the MPU if you install the Simpsons EPROMs when you move it over from SW.