In an earlier post, I explained how to replace the RAM and eliminate the risky batteries for latter model pins:

https://pinside.com/pinball/forum/topic/installing-barakandls-nvram-battery-eliminator-vids-review

But what can you do if you have a Classic Bally or SS Williams?

Get a NVRAM module that fits in the 5101 RAM socket.

There are a bunch of these on the market, but this module is only $14 ($12 in a 10 pack), so it's priced right.

http://nvram.weebly.com/

Here you can see the module.

It is basically a Ramtron FM16W08 surface mount NVRAM, mounted on an adapter board, with a supporting capacitor.

The adapter board allows the chip to be installed in the 5101 RAM footprint.

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Here is the underside of the adapter.

These are the pins that will be inserted into the RAM socket.

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Here is a Bally -35 board.

It is the most popular MPU board ever made, so I figured it would be a good test subject. If I can get a few more of these NVRAM modules, I'll post the installation instructions on how to install them in some other MPUs like the different Williams versions.

On the Bally -35, you want to cut the battery off first (Ideally, you cut the battery off the day you got the game).

Clean up any battery corrosion before going further, as it keeps corroding the board, even after the batter is gone.

The 5101 RAM chip is directly above and to the left of the battery.

CAREFULLY pry the chip from the socket with a flat screwdriver. Lift from one side, then the other.

If the RAM easily falls out from the socket - replace the socket. A good socket will give resistance to chip removal.

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Save the old RAM chip on a block of anti-static foam.

You can use it to troubleshoot another game.

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There is a big resistor next to the RAM socket.

If this resistor has been replaced, the tech probably mounted it high off the board so that it could have good airflow around it (it does get hot). Bend the resistor a little so it does not touch the NVRAM module.

If this resistor is burnt looking, replace it now with an 82ohm 2w, and make sure you mount it off the board with lots of air space around it.

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The module needs to be installed in the correct orientation. Do not mount it backwards.

Make sure the RAMTRON chip is on the "pin one side".

The module should be marked with PIN 1 somewhere on it, so people don't mess it up (hopefully the next batch of circuit boards corrects this omission) .
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Power up the game.

You should get one quick flash, followed by 6 flashes if everything is good.

You will lose your high scores and sound settings, so be prepared to spend a few minutes reprogramming the game.

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That's it.

You now have no batteries to constantly replace or leak.

Highly recommended!

http://nvram.weebly.com/

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INSTALLING NVRAM ON WILLIAMS SYSTEM 4 MPU
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There is a 50/50 chance that your system 4 MPU has had it's RAM replaced in the last 40 years, so you may or may not find an IC socket on the board.

This board looked to be almost a total virgin, only the battery pack had been removed and a remote battery connector had been installed.

Because the board was a virgin, we needed to install a socket.

The existing RAM was still good, so I kept it for future service swaps and put it on a piece of anti-static foam.

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Next, I unsoldered the old RAM.

Note that Pin 1 on the board is marked with a small numeral.

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I got a nice Dual Wipe IC Socket from Andrew.

Dual wipe means that the socket makes contact on both the front and rear of the IC legs.

If you don't like SIP Sockets, Dual Wipe is a great choice.
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Next, I soldered in the new socket.

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Finally, I installed the NVRAM module.

Note that pin one on the module corresponds to the pin 1 marking on the circuit board - this is important.

Power up the game and you are good to go - never having to worry about dead batteries again.

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Single wipe are the wost type of socket. One side of the IC leg touches the plastic frame, the other touches the conductive pin - so you are getting only half of the surface contact.

Dual wipe, you get contact and positive spring pressure on both sides of the IC leg.