Hi. I am refurbishing a Sega The Lost World Jurassic Park and have a DMD that behaves strangely. Sometimes it is normal, and other times it has parts dimmed out or patchy. I have replaced the ribbon cables, replaced the DMD with a known 100% one, and checked the power output of the display power supply. While the voltages aren't at the top of the range they appear to be within spec and there is a 12v difference between pins 1 and 2. I took these measurements with the display connected.

What do the tech gurus here advise?

Here are pics of what I am talking about..

Normal behavior in DMD test (vert. line out is the scanning line during the test) and Portals menu:

Portals menu normalDMD test normal

Patchy/Dim behavior at other times:

patchy switch matrixpatchy version screen

Beuller?

Thank you all for your replies and advice.

Yes, several times, and replaced all of the ribbon cables.

I took the DMD from Lord of the Rings and it behaves identically.

This was my suspicion and I will engage my electron vision and post power supply pin voltages with and without the display connected tomorrow. I have ordered a bunch of components to rebuild the power supply assuming that this will be the issue. The logic appears to function correctly for the rest of the game.

I have installed the DMD from LOTR with identical results. This eliminates the display as the problem.

I have installed the display power supply from LOTR with similar results. The lower right corner of the switch matrix screen are still dim but they 'fade in'. Other screens show the exact same dim sections as before. Below is a short movie clip showing this effect. This eliminates the power supply as the problem.

Next I will install the DMD controller from LOTR, which will have eliminated everything except the power supply wires and the display ROM.

I have wiggled the power supply wires from end to end with no change in behavior.

The currently installed Display ROM is 201 from IPDB.org, which also comes with the CPU ROM 202 that I have not been able to make work. But that is an issue for another thread.

Well, I'm a dumb ass. Not sure what I was doing before but I just swapped in the DMD from #lord-of-the-rings and it works great. Thanks for everyone's help and advice, I'll mark this as resolved.