Most pinball machines produced after 1977 have some sort of battery in the machine. The battery is used for to back up the memory of various information, such as high scores, quarters through coin mechanism, total plays, etc. When these batteries get old they can and will leak, causing a very expensive circuit board repair. It’s important to change your batteries before their date codes expire but the best practice is to get in the habit of changing the batteries every year. This will help you avoid that costly service. I typically do dozens of service calls because of battery leakage damage, and the most common response from my customers is that they didn't know their machine even had batteries. The excitement of getting a new game can often blur the memory, but use this guide to help keep your pinball machine in good working order.
The battery compartment is located in the head, behind the backglass. Williams and many Bally games use 3 standard alkaline AA batteries. The key to unlock the head is inside the front door hanging on a hook. Locate the key, insert it in the head lock and turn about 1/4 turn. The backglass will now lift up and out to expose the lamp panel. Lift the lever on the right side and swing the panel open. You should be able to see the batteries in their holder. If you change the batteries carefully with the game turned on, you will save your settings (including free play) and high scores. If you choose to be more careful and turn off the machine, your settings will be lost. Refer to your manual or call me and I will help walk you through the steps to return to free play. Lastly, if there is any corrosion on the batteries when you removed them, the circuit board will need to be removed and at least a new battery holder installed.