Pinball Circuit Board Repair And Restoration

When I say circuit boards I mean all the boards located in the backbox (Figure 3.1 – 3.4), and any located in the lower cabinet. Most circuit boards will be green, and some will be red. For clarification, I also include the player displays, or dot matrix display in the circuit board category.

These components are as important as your upper and lower playfield, as they are the brains of the operation. If they are not functioning correctly, nothing else will be.

Some of the most common problems found in the circuit board area is battery corrosion, expired filter capacitors, burnt &/or brittle connectors, bad IC sockets, cold solder points, broken fuse clips, poor ground lines, and required safety modifications.

I always start with the power distribution / rectifier board (Figure 3.5 – 3.7), as it takes all the different AC voltages and converts them to DC, which is what most of the game circuits operate off of.

Once this board is rebuilt (Figure 3.8), and it’s output voltage is all within proper operating specifications, then and only then can I move forward with powering up the other components. At this point any other issues will reveal themselves, and can be corrected.

Many problems on these boards are connector related (Figure 3.9 – 3.10). I spend lots of time changing out connecters, and both have to be done, the male pin, on the board, and the female in the connector housing.

Each board is pulled out one at a time, and all solder connections are re-flowed, board mounted battery packs are removed, and remotely mounted (Figure 3.11 – 3.12), with a quick disconnect. Many board issues were caused by pinballs being stored away for years with the batteries still in place. Batteries over time leak fluid, and gases. I’m sure we have all seen the damage done to old radios or toys that had the batteries left in them; it’s the same for pinball machines. For those that are wondering what the batteries are for, well they hold things such as the high score thresholds in the memory, and game parameters such as free play and so on.

On all early Bally & Stern games I remote mount a custom made bridge rectifier board (Figure 3.13 – 3.14). The original 3 bridge rectifiers were very under rated for the job required of them. (8amp-200 volt) When they fail, they are very hard to replace, requires much de-soldering, basically a service call. The 3 new bridge rectifiers (50 amp-1000 volt) if they ever fail, are function identifiable, and easily changed.

Player displays on many of the older games will be what’s called gassed out. These cannot be repaired. The industry now has access to new LED displays that require much less power, which provides greater reliability; as the high voltage section on the power supply can be turned off, as it’s only function was to provide power for the plasma displays.

Again, I’m not going to go into huge detail, just trying to let you know the care that goes into each rebuild / restore here at Absolute Pinball.