No Battery Mod for Y-Unit, and other Arcade Boards

A while back I worked out a drop in RAM replacement on the Midway Y-Unit Arcade hardware.

Anyone who collects arcade PCBs knows that Batteries Suck. Not only can they die and wipe out your highscores and settings but they can also leak and cause damage to your PCBs. I’m always on the look out for a good solution

On the Midway Y-Unit and T-Unit hardware the high scores and settings are stored on a Sharp LH5168-10L. I’ve also seen MOSEL MS6264L-10PC used. This chip receives power from the battery when the board is off so that it can retain it’s memory.

Ramtron FM1608 is a drop in replacement for these chips and does not need battery power to retain memory; meaning you can ditch the battery.

Y-UNIT Games
– Mortal Kombat (Y-Unit Version)
– Smash TV
– High Impact Football
– Super High Impact Football
– Strike Force
– Terminator 2: Judgement Day
– Total Carnage
– Trog

Instructions:
1. Remove Battery
2. Replace U49 with FM1608 DIP

T-Unit Games
T-Unit Game use a similar chip unfortunately the circuit for Writing is not compatible with the FM1608. someone has found an alternative using Cypress/Simtek STK12C68 though.

IT32 Games
I’ve noticed these chips used on Incredible Technologies 32-Bit hardware for games such as Street Fighter The Movie, Various Golden Tee revisions, etc. I haven’t tested this mod on these games yet but I would suspect some of these and more PCBs can use this chip to get rid of the battery.

If you know of other boards that could potentially use this FM1608 to get rid of the battery please let me know. Also if you know of similar mods with different chips on other hardware I’d love to hear about that too.

Some Notes to keep in mind:

1. I should note that they make this chip in both a DIP package and a SOP (surface mount) package so make sure you buy the right one.
   
2. Depending on the PCB setup it may not always drop in without additional modifications. The original Sharp LH5168 for instance had a “CE2” pin that is a secondary enable pin that must be set to turn the chip on. That isn’t present on the FM1608. On the Y-Unit and T-Units however the PCB is setup so that that pin is tied to a voltage source at all times, negating the need for any additional modification.
   
   The no-battery mod on the Sega Saturn actually uses the SOP version of this chip and if you’re familiar with the no-battery mod for the Saturn you know there are additional modifications that need to be made for that to work.
   
3. Not Every Sharp LH5168 or MOSEL MS6264L-10PC needs to be replaced; in-fact, some shouldn’t. The Sound boards on the T-Unit and Y-Unit games have another instance of this chip, but it doesn’t store anything important that needs to be retained during power off; it’s probably best to let that chip get cleared when the board powers down.