Something no pinball owner wants to see when they take the backglass off their machine is a set of bleeding batteries. The damage they cause can be fixable, but is often expensive either with board repairs or replacement boards. This is preventable with regular changing of the batteries, but is something so easily forgotten. (photo courtesy of peakpinball.com)
There are a few solutions to prevent this, but in these cases where there is an existing AA battery holder on the CPU board, I like to install a remote battery pack. It can be installed into the existing AA battery holder on the board. I like this solution since it requires no soldering and leaves the board completely untouched. Putting together the parts to build one is easy and cheap.
The wooden dowel is combined with the connectors, wire and screws to create a set of fake batteries that will plug directly into the AA battery holder on the CPU board.
In this case I’ve used a 4xAA holder, so had to add a pass through wire on the first battery slot. I went with this option since it’s enclosed and the 3xAA holders I came across were not. Having the holder close the batteries in adds some extra protection should the batteries be forgotten and start to leak.
The fake batteries are then soldered to the battery pack wires to complete the kit.
On older pinball machines, the battery installed on the CPU board is rechargeable and the above remote pack needs a slight modification. Instead of the pass through wire, a blocking diode needs to be installed, which prevents the charge going into the batteries while the machine is off.
The completed remote battery pack then simply installs into the existing battery holder on the CPU board. No soldering or board modifications required and quickly removable if needed. Note that the spots the fake batteries sit in will vary between machines, depending on how the battery holder is wired on the CPU board.
I like to do the remote battery packs in batches and then package them away for the next few machines I work on. I also sell them from time to time when requested.
Not all CPU boards have the AA battery holders installed on the CPU board, but the same battery pack can be used, only the wires are soldered onto the board. These are the ones where the blocking diode is usually required instead of the pass through wire. Installing something like this removes any danger of battery leakage across the Pinball machine PCB’s and if the batteries do leak, you only need to replace a $3 battery holder. All up they each cost around $7AU to make, so are a nice cheap option and will prevent any damage to PCB’s in the head box.