Demolition Man
Williams, 1994Hey guys. I just bought a Demolition Man with a non working DMD. While testing voltages on the DMD I looked away for a split second and bridged the 62 volt pin to the 12 volt pin. Optos went out and the game started launching balls continuously. F116 fuse was blown. I turned the game off replaced the fuse and it blew again right away on start up. I pulled the board and BR5 bridge seems to be fine. Where should I be looking next? U20 chip?
If you want to be sure it's the board then pull J116, J117 and J118 and if the fuse still blows it's on the board. Odds are good that it's on the board.
The circuit is quite simple. The bridge rectifier is rated for 35A and 200V. The capacitor is rated for 15,000uF but only 35V.
I'm sorry to hear this happened to you, the bridge rectifier will be fine as it was immediately placed into a reverse biased condition, Unfortunately, the list of potential damage is quite large as F116 didn't blow until other components on your +12V line failed in a bad way.
Parts that were hit with 62V:
Fliptronics II board - LM339 absolute max voltage = 36V
Trough boards - LM339 absolute max voltage = 36V
7 Opto board - LM339 absolute max voltage = 36V
DC Motor control board - LM7805 absolute maximum voltage = 35V
All optos and boards with optos - Flipper boards, trough transmitter, claw opto board, elevator opto board
Quoted from DumbAss:pull J116, J117 and J118 and if the fuse still blows it's on the board.
Thanks! Pulled J116, J117 and J118 and the fuse did not blow on power up. Do you have a recommended order to go in to start narrowing down the culprit?
Quoted from DumbAss:If you want to be sure it's the board then pull J116, J117 and J118 and if the fuse still blows it's on the board. Odds are good that it's on the board.
Quoted from fabsj82:Thanks! Pulled J116, J117 and J118 and the fuse did not blow on power up. Do you have a recommended order to go in to start narrowing down the culprit?
Put them on one at a time (with the power off) ... my guess is J118 will blow the fuse. Does your 12V LED on the power board light?
Actually, if you were checking this on the DMD, you likely only blew out your DMD board as the DMD controller board has a blocking diode on the 12V line which would prevent the 62V from back feeding to your power board. Try just leaving the DMD display disconnected
Quoted from Pin_Guy:Does your 12V LED on the power board light?
All LEDs match my Getaway except LED3 is lit solid and light on DMD driver board is off.
IMG_20200224_182019 (resized).jpgQuoted from Pin_Guy:Try just leaving the DMD display disconnected
That was the first thing I tried. Fuse blew right away
Quoted from Pin_Guy:my guess is J118 will blow the fuse.
J117 is my fuse blower.
Your +12V only passes through the Dot Matrix controller, I'm surprised these components didn't block it....
I may have misread the specs on display driver board Zener Diode D8 (1N4742), it may be shorted and sending your 12V to ground, disconnect J606 on the display driver to verify.
pasted_image (resized).png
Quoted from Pin_Guy:disconnect J606
Disconnected j606 and plugged in j117. Fuse did not blow. What are the chances I blew up my display as well? Of course I had my one known good one in there at the time.
Quoted from fabsj82:What are the chances I blew up my display as well? Of course I had my one known good one in there at the time.
I've never worked on one, but since that's your operating voltage several on the IC's on the board, I would give it a high probability.
As far as the Controller board, I would test both D7 and D8 with your meter in diode test. D7 is probably ok but it did push a lot of current, personally I would just replace both D7 and D8.
EDIT: After reviewing the schematics a bit further, the above statement only applies if your display has a Babcock driver PCB; if you have a Cherry PCB board, it has no connection to +12v as it uses +5V for all IC's so it should be fine.
Important information!
After reviewing the schematics a bit further, the above statement only applies if your display has a Babcock driver PCB; if you have a Cherry PCB board, it has no connection to +12v as it uses +5V for all IC's so it should be fine.
Quoted from Pin_Guy:Babcock driver PCB; if you have a Cherry PCB board
IMG_20200224_193923 (resized).jpgQuoted from Pin_Guy:I have no idea
Lol. Thanks a ton @Pin_Guy I really appreciate all your help. I'll take this as a win for the night. I can start a game, flippers are acting weird but I should be able to take it from here. Thanks again!
IMG_20200224_192529 (resized).jpgQuoted from fabsj82:Confirmed. Vishay APD=128G032 DMD does not use 12V. I dodged a bullet!
For sure, only out one $0.26 diode 
Wow! A really great repair log so far. And a reminder I need to buy better test leads for my multimeter. Yikes!
Quoted from BC_Gambit:I need to buy better test leads for my multimeter.
Definitely don't rely on notches in the probe and don't have three kids running around the machine while you are using it 
IMG_20200225_201602 (resized).jpghttps://www.amazon.ca/Automotive-Insulation-Crocodile-Multimeter-Certificate/dp/B07489TJMS
Hopefully that link works
Some of the pieces in this kit look like a good upgrade for me. Others might even have a better idea.
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Green Bay, WI
