Alky
New member
Anyone have this error message come up on their machine??? I cannot for the life of me find the problem. I hear it may be an Ic lm339?
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Some may have suggested, but you may have a bad chip at U20. U20 is socketed from the factory on RS, so pop in another ULN2803.
What I would do first is check all the switches on the shorted row. The switch matrix chart should be on the backside cover of the manual, or you can probably pull it off of ipdb.com. Do any switches in that row look like they have wires touching where they are not supposed to? Any diodes shorting? Do the switches look mangled in any way?
Another quick thing you can do to troubleshoot this is to pull the column and row connectors off of the CPU board. These are the green wires and the white wires. Go into switch matrix test after you unplug those, and see if the row is lit up. If it is, your prob is in the board.
Good luck,
-Mike
I would personally start looking for a short. Like a switch lug touching a bulb socket - something similiar.
EDIT - FWIW I just found this:
"
[FONT=Geneva, Arial, Helvetica, san-serif]WILLIAMS / BALLY PINBALL Ground Short on any row in the switch matrix
will certainly cause a serious malfunction of the game. The most common origins of
the ground short are: !. A faulty column driver on the CPU board (ULN2803 ). 2. The
Slam Switch in the coin door is mounted with two screws, which sometimes can short out the blades of the switch to ground. Disconnect the slam switch and see if the ground short disappears. 3. A faulty Opto Switch Board can also cause ground short. Disconnect the board and see if the ground short disappears. "[/FONT]
Man I feel your pain. Make sure that you put the U20 chip in correctly. When you plug it in the writing on the chip should be upside down. If that doesn't work do you have another game with the same CPU board that you can swap and test? If not and you think it's the board there are a few people that you can send it off to to get repaired. Clive at Coin Op Cauldron is one of the best. Here's Clive's email.
[email protected]