One way to test Bally solid state solenoids and their drive transistors is
to attach a test clip to ground and then use the other end of the clip to
ground the large metal tab of each transistor you wish to test. In some
ways this is easier than using the test button on the front door. It makes
it easy to retest a specific solenoid, and it helps you verify the correct
This technique does you no good if the transistor is bad, the solenoid is
bad, or the connection to the solenoid is bad.