Bally Solenoid Driver Board Upgrades/Repair

Trying to keep updates going as regularly as possible here, but has definitely been a busy few weeks. Last couple weeks have included doing two full flipper rebuilds including coils on a Data East Hook and DE Simpsons, fixing a power supply issue on a Bally Rally X, fixing a missing flash lamp 20v on a WPC board from a Creature from the Black Lagoon, a full restore on a Bally Strikes and Spares in progress, a T2 arcade board look over which ended up being a dead 3v battery powering the RAM and a High Speed with a blown solenoid fuse.

One thing I’ve done a lot of recently that I wanted to write up a quick post on is the Bally Solenoid Driver Board from Bally games manufactured from 1977-84. I have done the recommended upgrades and repaired four of these over the past month or so. The games I’ve done them on have been KISS, Paragon, Bobby Orr’s Power Play and Strikes and Spares.

This board is responsible for driving the under playfield solenoids and relays, regulating the high voltage for the displays and regulating the 5vdc logic voltage that is supplied to the rest of the boards.

Original C23 -- over 30 years old, needs replacement!

Original C23 — over 30 years old, needs replacement!

The first thing I always do is replace the C23 filter capacitor, which is the largest cap on the board. This cap is the one that filters the 5vdc logic, so its very important that it functions correctly. Most caps have a lifespan of about 10-15 years; with these games being over 30 years old, if that original capacitor is still on the board, it’s high time for a new one!

The other two modifications that are important for this board are: tying the negative lead of the replaced C23 capacitor to ground, and tying a jumper between TP1 and TP3.

While I have the board out, I always test all the transistors down the line to make sure they

Jumper on solder side of TP1 to TP3.

Jumper on solder side of TP1 to TP3.

are all good to go. Testing the TIP120 transistors is easy, just set your DMM to the diode setting, put the black lead on the large metal tab of the transistor and then the red lead on each of the side legs. Each leg should read .4 to .6 volts, any reading outside of this range means a failed transistor. If you do find a failed transistor, I recommend replacing the original failed TIP 120 with the sturdier TIP 102 transistor.

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About Matthew Mandarano

Matthew is a cinematographer and video specialist by day and pinball fanatic at night. Somewhere in between he also finds time to play the guitar, collect vinyl records and watch a good deal of movies and TV shows.
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