Pinball Troubleshooting Tips

OTHER LINKS : Repairing Williams/Bally WPC Pinball http://www.marvin3m.com/wpc/index1.htm

Williams/Bally Pinball Machines WPC and WPC 95 Systems

WILLIAMS / BALLY PINBALL FLIPPER COIL IS OVERHEATING, WEAK
FLIPPER, FUSE INTERMITTENTLY BLOWS, FLIPPER COIL BURNS:

A defective flipper opto switch can cause this problem. The coil will overheat
after a period of playing and can burn. The flipper fuse can intermittently blow.
The players usually complain that the flipper becomes weak. Check the opto
switch with your multimeter. Measure directly on the flipper button opto board
connector pin marked SW1 and SW2 against ground. You should measure
below 0.7 volts (below 1 V is still fine) with the button pressed. Higher reading
means a dirty or defective opto switch. If cleaning does not remedy the
problem (blow off the dust and use clean paint brush, don't use any cleaning
sprays ), replace the opto switch. Later models of Williams/Bally pinball's use
Schmitt Trigger opto switch (tree legs on the receiver side) which eliminates
this problem. Replace the coil if it looks like it has been severely overheated.

TWO OR MORE BALLS KICKED TO THE PLAYFIELD OR THE MACHING KEEPS
KICKING ONE BALL AFTER ANOTHER

WILLIAMS / BALLY PINBALL Complaints that two balls were kicked to the
playfield instead of one, or the balls are continuously kicked to the playfield,means a problem with the trough assembly opto switches. Check them in the Switch Edges Test. The test should indicate all trough switches are close 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 a 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 that fails under vibration. Also Tap the connectors. Machines around the time of Indiana Jones had problems with resistors and LEDs on the transmitter board breaking off. If a particular trough switch is not working measure the voltage directly across the LED. If you measure 0 V it most likely means that the resistor is open circuit or not connected to the LED. If you measure around 12 V, the LED is open circuit or not connected -- replace it. Around 1.2 V is the correct voltage.

SWITCH MATRIX PROBLEM - GROUND SHORT ROW NO.:

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.

THE MACHINE BLANKS OUT DURING THE GAME PLAY:

WILLIAMS / BALLY PINBALL

1. DIODE ON FLIPPER COIL IS OPEN CIRCUIT OR BROKEN OFF:

Check quickly all diodes on the flipper coil. The diodes are suppressing back EMF that can interfere with the computer system. A broken off or open circuit diode is a good explanation for the problem. Grab the diodes by your fingers and pull them (switch the machine off for your safety). They may look well connected but come off when you pull them. To check for an open circuit you would need to disconnect one end of the diode from the coil. I would not rush to do it; they don't become open circuit that often and if the machine has four flippers you would need to disconnect eight diodes and this is a bit of hassle. It is more common that a defective bridge rectifier as described in the following paragraph causes the fault

. 2. DEFECTIVE BRIDGE RECTIFIER BR2 ON THE POWER DRIVER BOARD:

If the flipper coil diodes are OK another common cause is a defective bridge rectifier BR2 on the Power/Driver Board. This rectifier is part of the +5V power supply and one of its diodes becomes an intermittently open circuit. Instead of full wave rectification we get half wave rectification and thus a lower voltage for the input of the +5V regulator. The bridge rectifier may appear fine when checked with your multimeter. But if the machine does blank out and you checked all diodes of the flipper coils then replace the rectifier. You have a good chance that it will fix the problem. Also, it is easy to damage the tracks on the circuit board if you are not sure how to do this; it's not worth the damage. You are better off to get it done. In WPC 95 machines the bridge rectifiers are created by individual diodes and we did not experience this problem.

Home

Williams/Bally Pinball Machines WPC and WPC 95 Systems
WILLIAMS / BALLY PINBALL FLIPPER COIL IS OVERHEATING, WEAK FLIPPER, FUSE INTERMITTENTLY BLOWS, FLIPPER COIL BURNS:
A defective flipper opto switch can cause this problem. The coil will overheat after a period of playing and can burn. The flipper fuse can intermittently blow. The players usually complain that the flipper becomes weak. Check the opto switch with your multimeter. Measure directly on the flipper button opto board connector pin marked SW1 and SW2 against ground. You should measure below 0.7 volts (below 1 V is still fine) with the button pressed. Higher reading means a dirty or defective opto switch. If cleaning does not remedy the problem (blow off the dust and use clean paint brush, don't use any cleaning sprays ), replace the opto switch. Later models of Williams/Bally pinball's use Schmitt Trigger opto switch (tree legs on the receiver side) which eliminates this problem. Replace the coil if it looks like it has been severely overheated.
TWO OR MORE BALLS KICKED TO THE PLAYFIELD OR THE MACHING KEEPS KICKING ONE BALL AFTER ANOTHER
WILLIAMS / BALLY PINBALL Complaints that two balls were kicked to the playfield instead of one, or the balls are continuously kicked to the playfield,means a problem with the trough assembly opto switches. Check them in the Switch Edges Test. The test should indicate all trough switches are close 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 a 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 that fails under vibration. Also Tap the connectors. Machines around the time of Indiana Jones had problems with resistors and LEDs on the transmitter board breaking off. If a particular trough switch is not working measure the voltage directly across the LED. If you measure 0 V it most likely means that the resistor is open circuit or not connected to the LED. If you measure around 12 V, the LED is open circuit or not connected -- replace it. Around 1.2 V is the correct voltage.
SWITCH MATRIX PROBLEM - GROUND SHORT ROW NO.:
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.
THE MACHINE BLANKS OUT DURING THE GAME PLAY:
WILLIAMS / BALLY PINBALL 1. DIODE ON FLIPPER COIL IS OPEN CIRCUIT OR BROKEN OFF: Check quickly all diodes on the flipper coil. The diodes are suppressing back EMF that can interfere with the computer system. A broken off or open circuit diode is a good explanation for the problem. Grab the diodes by your fingers and pull them (switch the machine off for your safety). They may look well connected but come off when you pull them. To check for an open circuit you would need to disconnect one end of the diode from the coil. I would not rush to do it; they don't become open circuit that often and if the machine has four flippers you would need to disconnect eight diodes and this is a bit of hassle. It is more common that a defective bridge rectifier as described in the following paragraph causes the fault . 2. DEFECTIVE BRIDGE RECTIFIER BR2 ON THE POWER DRIVER BOARD: If the flipper coil diodes are OK another common cause is a defective bridge rectifier BR2 on the Power/Driver Board. This rectifier is part of the +5V power supply and one of its diodes becomes an intermittently open circuit. Instead of full wave rectification we get half wave rectification and thus a lower voltage for the input of the +5V regulator. The bridge rectifier may appear fine when checked with your multimeter. But if the machine does blank out and you checked all diodes of the flipper coils then replace the rectifier. You have a good chance that it will fix the problem. Also, it is easy to damage the tracks on the circuit board if you are not sure how to do this; it's not worth the damage. You are better off to get it done. In WPC 95 machines the bridge rectifiers are created by individual diodes and we did not experience this problem.
Home