My newly purchased RCT has a progressively dying dmd. When it first arrived, it was displaying scores, etc., but the display started showing randomly blank areas that became progressively worse. Knowing little about these, I began troubleshooting as follows:
Checked all data and power cable connectors and reseated.
F Molex connectors to dmd ps were all renewed with new crimps.
Ps voltages: display connected, power on at dmd P1, pin1: -112vdc 2: -100vdc 6: 5vdc 8: 67vdc.
Swapped display into working DW, display better (higher voltages in Bally), but appears outgassed.
Ok, now the real trouble begins.
Swapped working DW dmd into RCT. On power up display now shows Stern Pinball, Coaster Tycoon, Display version a7.01, THEN GOES BLANK.
It didn't do that before I renewed the molex pins, and yes, I got them back where they belonged, triple checked before power up
Double checked display reinstalled back in DW. Ok.
Pulled driver bd Rom, checksum 02FD8DDB, Verified against downloaded Rom image, ok.
Pulled CPU Rom, cksum 00C1E5FF, verified ok.
Reseated everything with sockets.
Looked at signals from driver to dmd, (oscilloscope). Serial data runs while boot screen is on, then quits. (Flatline).
I can hear the slight squeal while the boot screen is on, quiets completely when blankout.
Dmd never lights up again until reboot.
Software problem? I definitely don't understand all that I know about that.
From the cpu at J1 on the driverboard I see reset low transit to high on start, strobe goes high, and pulses low at intervals, busy transits high for 30us at intervals, same for sat3. Stat2 and 1 no activity (low), stat0 transit high 30us. I see no activity on the data lines, only a constant approx .6vdc.
It feels like whatever program section that runs the display is not starting. I'm way out of my depth here, and cannot find any help in the big, fat stern service manual. I have no clue what the sequence of signals should be to start this thing, nor even what is controlling that sequence.
The diagnostic test buttons give bleeping sounds, but no display.
I have checked the driver for cold joints under a microscope, and didn't see anything obvious.
By the way, everything else on the machine works and plays normally. I can get guest credits, and the led display is perfect, just a black dmd.
I have been t'shooting with the outgassed board, but the results were the same when I used the good display.
Thank you in advance for any help you can give. I would consider a new display and driver, but I'm hesitant until I know where this problem lies