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Troubleshooting
Williams/Bally WPC System & System 11. |
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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:
- Faulty column driver on the CPU board (ULN2803).
- 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.
- Faulty Opto Switch Board can also cause ground short.
Disconnect the board and see if the ground short
disappears.
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