How To Get Rid of Those AA Batteries No More Ruined Circuit Boards!

by, 01/04/18. Copyright 2014 – 2018, all rights reserved.
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Pinball machines contain potentially lethal voltage.  Dangerous voltage may remain for a period even after it is unplugged.  Prior to opening a pinball machine, be certain to unplug it, then turn it on to insure that it was actually unplugged.  It is recommended that the machine be allowed to sit several minutes to allow any remaining power to dissipate. High voltages can be present on any machine, even unplugged, and it can be lethal. Read precautions before proceeding. Proceed at your own risk.

Note: Click on images for a larger photo.

AA batteries leak. They will ruin your CPU board if left in for too long. To make it unlikely to occur, replace your batteries annually. Yet even then, battery leakage can occur and ruin a board. So get rid of them!

There are five different options and which one is best for you depends on which game you own and your skill level.

1) Remote Battery Pack
2) Lithium Battery
3) Memory Capacitor
4) Coin Cell / Button Battery




Memory Capacitor

+ and - for the capacitor
The locations for the capacitor are indicated by the (+) positive, and (-) negative. Note that the capacitor has a (+) positive and (-) negative, too. Lightly use some fine sandpaper to remove the blue masking covering the bottom, ground, trace.

The best is to install a capacitor as this will never leak and is inexpensive. These are available at Great Plains Electronics (search for Part Number: CERS-1.5F-5V). These only work on early solid state pinball machines (see Pinwiki for a listing).

Capacitor battery
Capacitor Battery on an early Bally / Stern

Installation is easy (see photos above). Just remove the solder on the left side of where the battery used to be. Flow a little new solder in the hole so it will melt easier, then remove the solder with a solder sucker or wick.

Immediately below this spot, on the edge is the ground trace. That will be your second connection. Clear and clean a spot. Use fine sandpaper if necessary. Make sure solder will stick by applying a small amount to this ground trace.

Insert the positive (+) end of the cap into the positive (+) former battery hole. Don’t solder it yet. Solder the negative (-) side of the cap to the ground along the edge of the board while leaving the (+) in the battery hole. Solder the (+) in the battery hole.

Capacitor battery
Capacitor Battery on an early Bally / Stern
Memory capacitor
Memory capacitor installed.

You are done. Note that the board may not boot the first time as the capacitor has to charge. After a few seconds, turn off and try a second boot if needed. I have found that these capacitors keep memory for longer than 6 months with the machine turned off.

Remote Battery Pack

Remote battery pack
Remote battery pack.

Many pinball machines cannot use a capacitor. Generally, those machines with internal clocks drain a capacitor too quickly. These machines have AA batteries on the CPU. A remote battery pack keeps those AA batteries, but removes them from the playfield. Because these can still leak, they should be placed away and below any electronics.

Pre-made packages are available or you can make your own. When making your own, generally, the battery holder is removed and wires are soldered to connect the pack. It is a good idea to include a plug so that the CPU can be removed without the battery pack.

The disadvantages of the remote battery pack is that it is easy to lose the memory settings if the CPU needs to be removed, the batteries can still leak, and the AA batteries should be replaced annually – although that is not as critical.

Overall, remote battery packs are the least attractive of the options.

If soldering wires, the positive goes on the top right battery holder hole, while the negative goes to the lower left, as indicated in the photo.

Note that if installation of this pack is done with the power off, then the machine will lose all of its settings, so write them down. Pre-made packages have the dowels in place of the batteries. If performing this installation with power on, lethal high voltages are present (see ‘Caution’ above). Soldering, as shown in the above photo must be done with the power off and the CPU removed, so all settings will be lost.


RAM location
Location of the RAM in a Whitestar pinball machine Data East / Sega / Stern.

In an ideal world, all pinball machines should use NVRAM. But that did not happen, so we are stuck with dealing with batteries.

Bally / Williams CPU board. The RAM is the second chip with the white label on it, and it is soldered in place.

NVRAM stands for non-volatile random access memory. It does not need a battery to keep information in place. Unfortunately, the size that would fit our pinball machines is no longer available. So smart entrepreneurs have made adapters. They are not cheap but they do the job very well.

I recommend NVRAM if your RAM is in a socket. The good news is that most Data East, Sega and Stern (Whitestar) pinball machines have RAM in a socket. Just turn the power off, remove the old IC and insert the new one in the right direction (this is crucial). If you can pry out an IC, you can do this. Here is a chart listing easy and hard to do pins. Be sure to record your game settings first as this will erase everything.

Unfortunately, most later Williams / Bally pinball machines have their RAM soldered in place. Removing it and installing a socket is not easy.

Watch Battery Buttons

Watch battery buttons are the prefect replacement for AA in pinball machines where the RAM is not socketed. These batteries are known to last 10 years and rarely leak. The parts are cheap and installation is a 20 – 60 minute job. One has to be able to solder and willing to use a drill on your CPU board, but it is easier that it sounds.

Parts Needed:

1) Battery holders. I got a slew of battery holders from Amazon for next to nothing. Look for Button Battery Holder Case Black for CR/LIR2032 2025 2016, or something similar. Those numbers at the end are the battery numbers (types) that fit, in this case are 2032, 2025 and 2016.

2) Watch (button) batteries. I got several of the CR2025 batteries because they also fit several items that I use like a Fitbit. Get a good name brand as cheap imitations are common. They may not last long and could leak.

drill bit
1/16″ drill bit

3) A 1/16″ drill bit (~1.5mm).  A drill.

4) Pencil or sharpie.

5) Solder, soldering iron, and desoldering tool (wick or solder sucker).

6) Fine wire cutters.

7) Thin wire or left over clipping from a resistor.

Installation of the Watch (Button) Battery in Bally/Williams WPC89

WPC89 with battery pack removed
Williams board with battery pack clipped off

1) Record your pinball machine’s settings. This process will erase everything.

2) Turn the power off and unplug. Remove the wires connected to the CPU. Loosen, but do not remove, the screws holding the CPU in place. Lift and remove the CPU.

Find spot to drill
Locating the drill hole using the battery holder.

3) Remove the batteries (all your settings are gone! – see step #1).

4) Clip off the old battery holder with fine wire cutters. If you really want to, unsolder it, but these holders are cheap and poorly made. If you ever want AA battery holders, buy a new set.

WPC ground for battery
Ground on the board is this “grid” area. Check for that grid on both sides of the board before drilling!

5) Remove the solder from the top right hole. This is where the positive (+) voltage is applied in WPC89 CPUs. If doing this on another generation or manufacturer CPU, you will need to determine which hole to use.

Drill spot
Positive hole at the top. Drill hole and ground solder spot at the bottom.

6) Identify the positive (+) side of the watch (button) battery holder. Generally, the positive side is the edge of the battery.

7) Insert that lead into the positive (+) hole in step #5. Aim the other over the “grid” area on the board that is ground. Make a mark with a pencil or sharpie. Confirm that there is ground on the other side of the circuit board (crucial).  Caution: Do not drill unless there is a ground ‘mesh’ on BOTH sides of the circuit board.

Ground connection
Because the ground solder point was so close to the ground of the battery holder, it is possible to have solder run between the two, and not use a short wire.

8) Drill the hole. Confirm that ground is on both sides of the board. Locate a nearby ground solder spot.

Drill hole
Drill hole in the back (middle). Positive (+) at top. Solder spot at bottom. Note on this board, the drill hole and the solder spot are not close together.

9) Insert the battery holder. Be certain positive (+) side of the battery holder goes into the positive side on the circuit board.

10) Solder the positive (+) side of the battery holder to the board.

11) Solder the thin wire to the negative (-) side of the battery holder aiming towards the solder spot. Solder the wire to the nearby solder spot.  Or use a small knife and scrape away the green mask and solder to the copper on the board.

All done!

Wire jumper
Since the solder spot and the drill hole are not close, it will be necessary to connect the negative to the solder spot using a wire.

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