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Sega Large DMD Woes

E

Eddie Twadds

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10 Years
Joined
Nov 26, 2011
Messages
258
So picked up a Sega Frankenstein recently - more of a project than I had envisaged (one man's 7/10 isn't always another's) but I'm always up for a challenge! The large display was working but started resetting and flickering. Now the display does not boot at all. I understand this is due to the board requiring a good 5v supply.

The main power supply board has been extensively reworked. I have done the following:

  • Sega modification to get a better 5v source to the DMD. Service bulletin 106.
  • Repinned the DMD J1 connector and corresponding header.

I can now get 4.9v direct to the DMD but it still fails to boot. When I test the 5v output with the DMD connected this drops down to 4.8v - so not a massive drop but something is bringing it down.

I plan to replace the C5 header pins on the power supply board and change the BR1 rectifier to see if that improves the consistency of the 5v supply.

After that I am stumped. Any help gratefully accepted.
Martin
 
The good news is mate, if the dmd is dead, Dr Pinball do replacement LCD panels. Granted, not ideal but at least its not on the scrap heap
 
Have you tried powering it with a solid 5v supply from another source to confirm it still works? IIRC you can boot Sega displays on a test bench with just the display and display board
 
That's on the list of things to do. Also have someone with a Batman so will see if we can do a display swap.
 
Get another power supply (old computer psu?) to feed a seperate 5v to the display. If the display still fails then it's the display or pcb on the back of it that needs looking at, if not then it's something in the game pulling the 5v line down or possibly a dodgy fuse holder...
 
Definitely not ribbon cable related, as swapped for known working one. Also, 5 volts retested with everything else removed from the supply board @ steady 4.96v at all 5v outputs. This drops to 4.85v with the DMD connected. Can't see that changing BR1 (5v on the board) or BR3 which regulates the display voltage will give any benefit. Just need to rig an atx supply to test out the DMD out of the machine.
 
Right. No joy on firing it up on the bench. Clay suggests 12v and ground to the board via an ATX power supply. I presume I also need 5v to the driver board to generate the image? Going to try putting it into Batman at the weekend. Meanwhile lots of other woes. See separate thread. Less than chuffed this week with my new purchase which was sold as working...
 
Had same problem. Take the DMD out and put it in the bin ;)

Get a DMD extender and an old 17" monitor and make a new one. Drop me a pm if you need any help..
 
Have you looked at the 5v connector to the display driver PCb. This is the connector that causes the most problems. Before splashing out on dr pinball conversion, ensure that the driver board is good as this is still needed for the drp conversion.
 
Changed the 5v connector and pins. Previously it was directly soldered (so evidence of prior issues). Getting solid 4.95v at the pins, dropping slightly when dmd plugged in. Will drop.the board into mates batman - will it boot ok with batman cpu rom and Frankie display rom?
 
Good news :) the driver board works in another Sega large DMD pin. The bad news :( the DMD doesn't work with another driver board from the other Sega pin. Other than the Dr Pin conversion, what can I/should I look for on the DMD to try and fix. Presume it's a HV fault? Or should I just call it a day now and stump up for the LCD conversion?
 
JUST HOLD ON A DAMN MINUTE! The master is here to help you... :cool:

I put a Dr Pinball Colour DMD in my Batman Forever just recently and I think this was a major contributing factor to it's recording breaking sales price so I'd highly reccommend it. However, it wasn't cheap to do, plus at the time Dr P wasn't supplying the full kit, only the extender and SD card. So I had to buy the other components myself and finding the right stuff was a headache.

Things you can try before doing that:

Step 1: Do the SEGA power cable modification as in the service bulletin, but use trifurcon connectors as they connect to the header pins on 3 sides (I see you've done this already).

Step 2: Check for cracked solder joints on the power supply header pins and reflow any which look suspicious (I see you've done this already). This goes for the header pins on the DMD too.

Step 3: Clean the header pins with a fiberglass pen for good contacts.

Step 4: Replace your bridges. Bridge Rectifiers are one of the major causes of voltage drop in any pinball machine. At £2.50 a pop for uprated ones, replace them all. The one on the power supply board however is tricky to remove and you need good desoldering tools to do it cleanly.

Step 5: Recap your power supply board. New capacitors = clean voltage for happy circuits.

Step 6: Make sure the wires in your IDC connectors are correctly seated. You can usually trace where the voltage drop is occuring at this point.

The above should fix it. Otherwise just go with Dr P. Bang your old display on eGay and what you get for it should cover most of the cost of the new display. Good luck! ;)

- EDIT -

Forgot to say as well, make sure all the fuse connectors are tight. They are prone to failing. I usually replace them all.
 
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