Complaints that two balls were kicked to
the playfield instead of one, or the balls are continuously
kicked to the playfield means problem with the trough assembly
opto switches. Check them in the Switch Edges Test. The test
should indicate all trough switches closed if the balls are
removed from the playfield. Don’t forget to check the
"Upper Trough Switch" (Ball Jam Switch). This switch is
often overlooked. Trough problems are often intermittent.
Introduce bit of vibration to the transmitter and the receiver
board. Tap them with the handle of your screwdriver. The switch
Edges Test will indicate the switch which fails under vibration.
Tap also the connectors. Machines around the time of Indiana
Jones had problems with resistors and LED's on the transmitter
board breaking off.
If a particular trough switch is not
working measure the voltage directly across the LED. If you
measure 0V it most likely means that the resistor is open circuit
or not connected to the LED. If you measure around 12V, the LED
is open circuit or not connected - replace it. Around 1.2V is the
correct voltage.