Time is the Enemy... Preventing Battery Damage in Pinball Machines

Battery corrosion is one of the most common causes of damage to older pinball machines, yet many owners are unaware that batteries are fitted inside the backbox. Simon Haxton explains how battery corrosion occurs, why it can permanently damage circuit boards, and the practical steps owners can take to prevent it.

Most Williams and Bally pinball machines manufactured until the late 1990s used AA alkaline batteries mounted directly on the MPU board to retain memory when the machine was switched off. As these batteries age, they can leak, causing corrosion that damages nearby electronic components.

Preventing battery damage is far easier than repairing a corroded circuit board.

Simon's advice is simple: remove the batteries from the board as soon as you can. "Time is the enemy" if they're forgotten, particularly when machines are left unattended or in storage for long periods.

Another option is to replace the batteries with non-volatile RAM (NVRAM). However, NVRAM isn't suitable for every machine, particularly those that rely on a real-time clock. Twilight Zone has a clock attract mode, and any game that has a Midnight Madness mode needs to know when it's midnight. NVRAM won't keep the actual time of day. For some games, it is preferable to have batteries because of those features.

Lithium coin cells are another alternative to AA batteries and generally have a much longer service life. Simon recommends replacing AA batteries every two years, whereas a lithium coin cell may last 10 to 20 years.

Some Gottlieb games from the 1990s are still running on their original coin cell batteries more than 30 years later. However, the CR2032 batteries used in Jersey Jack machines can go flat after only a few years.

If a battery has already leaked, the alkaline residue can be neutralised with vinegar. Because vinegar is acidic, it reacts with the alkaline deposits and helps stop the corrosion process.

Cleaning alone doesn't always solve the problem. "The corrosion is like a cancer, and it creeps into all the traces and eyelets, and rots the metal parts."

Even after a board has been repaired, hidden damage can continue to cause problems. Replacement boards can be expensive or difficult to source, particularly for System 11 machines. "It's better to save the originals if you can."

Simon recalls seeing photographs of battery damage where the corrosion had "frothed and looks like toffee. It's not pleasant, and it's green."

Despite the severity of some cases, the problem is largely preventable. Simon recommends checking the batteries every two years and writing the installation date on each one with a permanent marker so they can be replaced before they go flat, and subsequently leak.

Batteries should also be protected from extreme heat and cold, as both can shorten their lifespan. Simon says Duracell batteries "leak quite easily", while other brands can be more reliable. However, he stresses that every battery will eventually leak, making regular inspection and timely replacement the best way to protect a machine.