Williams WPC-S lamp problem

THE COUNT

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On a Williams Dirty Harry, I have a lamp row that will not light. The row is J134-1.

- The TIP102 (actually it is a TIP122, I assume it and another one have been replaced with these) for this row, Q90, tests good according to the method suggested in the TOP repair guide (not having continuity with the ground strap in the backbox).

- There is continuity between the red/brown wires at the lamps and the header pin on the driver board, so the IDC isn't to blame.

- None of the associated lamps in this row light up when selected in the single lamp test.

Where should I go from here with this?
 
The lamp driver of this game has overcurrent protection built into the row drivers. You must make certain that none of the lamps/sockets/or diodes and thier associated wiring is not shorted out or touching some other wire. I've seen light bulbs short internally, never could figure out how but I've seen it!! Once you are certain that there are no shorts/faults you can get it into test mode and select that particular row, then ground J134-1 pin and see if they light. If so it's a board problem that needs futher trouble shooting.
 
This has been fixed.

There was no continuity between the suspect transistor's tab and the header pin for the unlit row. I removed the driver board, removed the solder from the transistor's pins and found there was no solder pad for the middle leg of the transistor. When the transistor was previously replaced they must not have noticed the pad was gone, a simple cap-leg jumper fixed it.
 
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