The Who's Tommy Pinball Wizard
Data East, 1994You're currently viewing posts by Pinsider monkfe.
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I recently replaced the caps on my Tommy power supply board, after reinstalling the board, my Power supply fuse for the DMD is blowing. I removed the power cable to the DMD, and I have all my power supplies on the board, plug in the DMD, fuse blows?....sort of coincidental that the DMD would just blow, I did find a bad transistor in the high voltage area of the board. Is this common for a DMD failure to blow the fuse ie shorting out? Thanks Gents.
Quoted from jgadzia:if you are only blowing the fuse when you plug in the dmd. the short has to be in the dmd or on the cable to the dmd.check and make sure no connectors on the dmd are touching something they shouldnt be.
Yeah that's what I thought too, maybe a screw dropped I to it, but all good.
Quoted from Inkochnito:The problem is not nessesarily with the display.
Removing the connector from the display just opens the circuit of the high voltage.
The fuse is connected to the center tap of the HV section and is in fact a return fuse.
Anything in the HV-section can cause the short.
A bad transistor can cause the short.
Do you have the oppertunity to test the DMD in another game?
Then you will know for sure.
I think the problem is your HV-section on the power supply board.
Hmmm would it work in my William's game...just enough to fire it up?...I'd have to check the connector pin out
Quoted from Crash:I've seen shorted DMDs before. Before you install the DMD in another game I would urge you to do a short citcuit test on all pins against ground. With the DMD removed from the game, take a multimeter and put it in ohms mode. Take your black probe and touch one of the the metal screw contacts on the DMD for your ground connection. The take the red probe and touch each high voltage power supply pin on the DMD. You should only get a beep/zero ohms/OL on the meter when touching the red probe on the ground pins (only pins 4 and 5). If this happens when touching any of the other pins, the DMD is shorted.
Pin 1: -125 volts
Pin 2: -113 volts
Pin 3: Key
Pin 4: Ground
Pin 5: Ground
Pin 6: +5 volts
Pin 7: +12 volts
Pin 8: +62 volts
I'll check it out tomorrow!
Quoted from Crash:I've seen shorted DMDs before. Before you install the DMD in another game I would urge you to do a short citcuit test on all pins against ground. With the DMD removed from the game, take a multimeter and put it in ohms mode. Take your black probe and touch one of the the metal screw contacts on the DMD for your ground connection. The take the red probe and touch each high voltage power supply pin on the DMD. You should only get a beep/zero ohms/OL on the meter when touching the red probe on the ground pins (only pins 4 and 5). If this happens when touching any of the other pins, the DMD is shorted.
Pin 1: -125 volts
Pin 2: -113 volts
Pin 3: Key
Pin 4: Ground
Pin 5: Ground
Pin 6: +5 volts
Pin 7: +12 volts
Pin 8: +62 volts
VCC, which is pin 6, 25 ohms, everything else off scale (meter set at lowest range), so I'm going to guess that its not shorting out? ...
So my color dmd came today, installed it, it powers up(able to see menu ect), but now my cpu won't boot. PIA is on steady (no blinking), but my blanking led never comes on...5v on as well. Book says 6821 may be bad, replaced all of them (rottendog board mind you). and still no difference....thoughts gents.
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Toms River, NJ