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twistedsymphony

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A while back I worked out a drop in RAM replacement on the Midway Y-Unit Arcade hardware. This came up recently in a convo I was having with a friend of mine so I detailed it on my blog: http://solid-orange.com/2051 and I figured I'd repost it here.

The original chip on my Y-Unit boards was Sharp LH5168-10L. I’ve also seen MOSEL MS6264L-10PC used.

Ramtron FM1608 is a drop in replacement on Y-Units…

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. 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.
 
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LittleLarrySellers

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Another cool tip @twistedsymphony !

Came upon this when my MK 2 board started failing because I glanced at it one day and that was enough to start this U49 CMOS error crap. Battery and battery holder replacement didn't work so thought I would try this. Still doesn't work... womp womp.. so something else is going on.

However, I bought a handful of these FM1608s and did my Smash and Total Carnage boards. Works like a charm! thanks for the tip. Both are recapped and now don't have a battery. A good feeling for me when my boards are in a state like that.

Once I get my MK2 working again (hopefully) I will def stick with this mod too on my T-Unit.
 

ekorz

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Just installed one of these. My MK1 thanks you! I don't remember what unlocks in mk2 or nbajam, but I want to try writing some unlocked data to the eeprom when I get around to replacing this on those boards. The guy in the klov thread talks about doing that, so maybe I'll ask him for his file(s).
 

twistedsymphony

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I've not had luck getting the FM1608 working on T-Unit. it throws a write error
supposedly the STK12C68 works on T-unit according to that KLOV thread though I'm not too keen on the way they wired the cap on pin1. I wondering if that is even needed or if pin 1 on the socket could be removed completely along with ignoring the other mods to allow it to work as-is

the cap is for auto-save on shut down, but theoretically that shouldn't be needed so long as you're not powering off in the middle of a write. the other jumpers are for the battery switch circuit, but it seems to me that circuit works fine with no battery installed normally, so why bother?
 

XtraSmiley

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Very cool! Is there a source for these cheap? I have Trog, STV, TC, and MK1.

And seconding the question on will this keep the unlocks for MK1. Not so concerned with MK1 as I am with MK1+.
 

XtraSmiley

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What unlocks?
Far as I know both MK1 and MK2 have nothing that is unlocked and saved.
Can you give a single exmaple?
No, I can't think of any (maybe something from the operator menu?), but I believe the team at MK+ has added them within their games as they are developed. I don't know if MK+ has them (yet), but maybe it's listed as "cheats" here:

https://www.mortalkombatplus.com/forums/general-discussion-mk/183-mortal-kombat-change-log-and-ideas

Also, I'm smoking a little crack as MK+ is only on a T-Unit and this above is for Y-Units (with no mods) so some investigation may be in order. Of course Paul, the guy working on MK+ is on a break right now anyway!
 

twistedsymphony

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We're discussing both Y unit and T unit. It's just a different chip depending on the platform.

Ive never used MK+, when you're on battery do the unlocks stay there between boots? If yes then this will will work.

Ultimately this will allow your pcb to work exactly as it does now... Just minus the battery.
 
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AlxUnderBase

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Since the only Midway pcb i have is a Mortal Kombat 2 , will be nice to do this mod even if now runs very well (i don't know for how long) with a new 2325 battery :happy:
 
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