MPU Battery Replacement Options

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1 Introduction

RAM chips are typically used to store game settings and bookkeeping data. However, RAM is volatile and can only store data if power is applied to the chip. If power is lost, so is the data. So, the solution to this was to include a battery on the MPU to retain the data in RAM when the game was turned off.

Unfortunately, many of these batteries leak and damage or destroy circuit boards in the process. So, it is imperative that the battery is removed from the MPU in order to prevent this damage in the future.

In order to retain the data for game settings and bookkeeping, there are a few different options to replace the original battery and prevent future problems from leakage.

This guide assumes that the old battery has already been removed from the MPU and any damaged caused by a leaking battery has been cleaned up and repaired.

1.1 Remote Battery Pack

The remote battery solution is when a battery pack is installed in a game, but lead wires are attached to the positive and negative solder points on the MPU. The safest place to mount a remote battery pack is below any circuit boards and as far away from them as possible, so as to avoid escaping gas and drippings from leaks.

1.2 Lithium Battery

Classic Williams games had a build-in battery holder that could fit AA batteries. Unfortunately, it was common to see standard alkaline batteries used in these holders, which always leaked.

Lithium batteries are produced in the AA battery footprint, so can be installed in the battery holders used on classic Williams MPUs. Lithium batteries are less prone to leaking, but it is still a good idea to mount them off the MPU in a remote battery pack.

Installing batteries directly onto the MPU leaves the game open to the possibility of an owner replacing a dead AA lithium battery with a AA alkaline battery if they don't have a lithium battery on-hand because it's the easy and lazy thing to do. As a result, battery leakage becomes a serious risk again.


1.3 Memory Capacitor

Memory capacitors are special capacitors that hold a charge for an extended period of time and take the place of a battery. The downside is that the game has to be turned on at least once for several hours every 14-30 days in order to build up to a full charge.

Additionally, lower quality capacitors are prone to leaking, though not as spectacularly as alkaline or NiCad batteries.

At this point, memory capacitors have fallen from favor because of the introduction and economical prices of lithium batteries, coin cell batteries, and NVRAM.


1.4 Coin Cell / Button Battery

Lithium coin cell batteries (also known as button batteries) are much less prone to leakage than the batteries originally used on MPUs. They typically have about a 10-year life span when used on an MPU. Gottlieb System 3 MPUs were the first to utilize coin cell batteries.

Note that while the risk of leaking is pretty small, they still can--and do--leak after enough time. Poor storage conditions are also sometimes a contributing factor.

Gottlieb System 3 MPU with a leaking coin cell battery


1.5 NVRAM

NVRAM (non-volitile RAM) is being used to replace volatile RAM installed on the MPU. Volatile RAM can only store data if power is applied to the chip. If power is lost, so is the data. NVRAM can retain data without needing any power. It is essentially "frozen" in the chip.

Various game systems use different types of RAM, so adapters are needed to adapt the footprint and pinout of the 6264 NVRAM pinout to the RAM footprint/socket that the game system is using.

NVRAM adapters typically list which RAM footprints/sockets and/or game systems they are intended to support.

1.5.1 Products

2 Game Systems

2.1 Allied Leisure

2.1.1 Generation 1

Game data is not saved. A battery solution is not necessary.

2.1.2 Generation 2/3

2.2 Alvin G

  • Remote Battery

2.3 Atari

2.3.1 Generation 1

Game data is not saved. A battery solution is not necessary.

2.3.2 Generation 2

2.4 Bally

2.4.1 -17/-35/-133 MPU

2.4.2 6803 MPU

2.5 Capcom

  • NVRAM

2.6 Data East

2.7 GamePlan

  • Remote Battery
  • NVRAM (not fully tested)

2.8 Gottlieb

2.8.1 System 1

NVRAM adapters are not currently available for System 1 games due to the mismatch between the address lines used on the MPU and standard 6264-based NVRAM.

2.8.2 System 80/80A/80B

2.8.3 System 3

2.9 Heighway Pinball

2.10 Jersey Jack Pinball

2.11 Sega

2.12 Spooky Pinball

2.13 Stern

2.13.1 MPU-100/MPU-200

Note: The MPU-200 uses two RAM chips and has two RAM sockets. Two separate 5101 adapters can be used, or an adapter that specifically accommodates this board can be used.

2.13.2 Whitestar

2.13.3 SAM

2.13.4 SPIKE

2.14 Williams

2.14.1 System 3-7

2.14.2 System 9

2.14.3 System 11/11A/11B/11C

2.14.4 WPC

Note: Games that utilize a real-time clock will need a battery instead of NVRAM to keep proper time. Otherwise, the date/time will not advance while the game is powered off.

2.14.4.1 Games Affected By a Real-Time Clock

WPC (Fliptronics II)

  • Creature from the Black Lagoon (different music plays based on the date)
  • Twilight Zone (clock on the playfield shows correct time)

WPC-S

  • Dirty Harry (midnight madness)
  • Johnny Mnemonic (midnight madness)
  • WHO dunnit (midnight madness)
  • Theatre of Magic ("hermaphrodite position" - midnight madness does not depend on real time clock since it is a game mode)

WPC-95

  • Congo (midnight madness)
  • Junk Yard (midnight madness)
  • NBA Fastbreak (midnight madness)
  • Medieval Madness (midnight madness, but special mode needs to be enabled to activate it)

2.14.5 Pin2000

2.15 Zaccaria

2.15.1 8060 MPU

2.15.2 Generation 1

2.15.3 Generation 2

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