I should give some background. I got this TFTC that needed put back together. I got that done and got a replacement MPU booting...
Found a couple bad transistors causing switch matrix problems, game is then working 100% for about two weeks. After playing about 40 games on it... Display goes out. Start testing fuses... I notice that quite a few are overfused badly. Once I get all the correct value fuses in the power supply, the 0.5 amp display fuse blows. I rebuilt the PS and high voltage part of the PS, 0.5 fuse still blows. I give up and buy a new Rottendog DPS004 power supply.
Today I installed the DPS004 power supply that arrived. 5VDC is low (4.7VDC). I install a 250K resistor per the instructions that shipped with the power supply. Now getting the proper 5.0-5.1VDC when tested on all boards in game. Still nothing on the display.
I swap working ribbon cables in from another game, no change.
I replaced the small 100uf 25V filter cap on the DMD controller board, no change.
I burned a new TFTC 27C040 display EPROM, no change. (Yes R11 is removed!)
I installed a new 68B09EP CPU in U11 of the DMD Matrix Controller Board, no change.
I installed a working MS62256L RAM into U8, no change.
I'm convinced that the DMD Matrix Controller is bad unless there is something I am missing. I don't have the ability to burn the custom PAL chips on that board and a replacement is $160+shipping.
Here are the voltages I currently get at the P1 connector of the display.
At all of the DMD controller IC's I get exactly 5.00VDC throughout the board.
Can I easily check anything else on the DMD controller with a handheld logic probe perhaps?
I'm fairly certain that the DMD will display the game's display ROM version even if no MPU/driver board is present in the game. So, I'm ruling out the MPU/driver board as the problem.