Bally 6803 Pinball Power Module Blows High Voltage Display Fuse

Here’s a Frank’s quick tip. I’m working on a Bally Beat The Clock pinball that’s unfortunately been abused. We just saved it from the “parts game” line. It’s had wiring cut out of the head, connectors cut off etc. It was also missing the logic board and power module. Otherwise it’s in good shape with a nice playfield.

I found a power module I had rebuilt back in 2015. It works but blows the high voltage display fuse. This system has both the input and output fuses on the power module as opposed to older games that have the input fuse on the rectifier board. The input fuse feeds directly to the rectifier diodes. The 6803 power module uses individual diodes instead of a bridge rectifier.

The thing with this system is that you can just replace the one failed diode. I never do this and I don’t recommend it, but if you want to you can, especially if you only have one diode on hand. The reason I don’t recommend it is because diodes are cheap and you should always have plenty on hand. They are used all over the game. On coils, on the switch matrix, the lamp matrix and other places.

The factory originally used 1N4004 diodes, which are adequate. I keep 1N4007 diodes on hand. They are a bit beefier and can handle up to 1000 volts. It’s overkill but what the hell? Go big or go home right?

These can be used just about anywhere on the game unless a specific type of diode is used such as a germanium diode used on older Gottlieb switches.

When the primary fuse for things such as lights and coils blows as soon as you turn the game on, look at the rectifier diodes first. They are what converts the reduced A/C voltage from the transformer to D/C voltage, are usually the first thing connected to the fuses and the first weak link.

If you look at my Bally Transporter post, you can see what happens when a diode fails but doesn’t cause a fuse to blow. Check it out here.

You can see in the pics below checking a good diode compared to one that’s shorted.

Checking a display high voltage 1N4004 diode on a Bally 6803 power module. This diode is good.
This diode is shorted. When reading diodes you typically will get about.500v in one direction and an open reading in the other.

I popped in a new diode and checked them all once again to be sure. It’s rare, but new parts can be bad. Just take a minute and throw your meter across the new diodes and save yourself a potential headache.

It sucks when you think you have something fixed only to later find out a replacement part is defective. You’ll find yourself wasting a ton of time looking for something else wrong with the circuit. Ask me how I know.

To finish up the board I replaced the high voltage capacitor and modified the fuse holder to accept a standard MDL fuse.
If you look closely you can see how I moved the fuse clip to allow a standard MDL fuse to fit.

To wrap up the job I installed a new high voltage capacitor, a 150uf X 350v and I modified the output fuse clip to allow an MDL fuse to be used instead of the shorter fuses installed at the factory.

I didn’t take pictures but I also replaced the 4 large diodes in the upper right corner on the pic above. Those are for the +5v line which is the logic power for all the boards. They work hard and get hot so if you’re servicing your board, throw in some new ones. I use 6amp diodes, the same ones needed on the power module for Baby Pacman and Granny and the Gators.

These are things I wasn’t doing back in 2015 so that’s why they weren’t done. I hope you found this educational and informative and if you have any questions or a problem I may be able to help you with shoot me an email to

Till next time, Frank

Readers Comments (1)

  1. Great and very informative post. Thank you!

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