The Art Of CPS2 Battery Maintenance

Introduction

This project is for owners of the Capcom CPS2 units who want to change their batteries in a simple and elegant manner.

To combat bootleggers, Capcom used encryption in their CPS2 based arcade hardware. The decryption key itself is stored in battery backed RAM. When the battery dies, the game will no longer work. Therefore it's important to change battery every 5-6 years to prevent the board from commiting suicide.

Changing the battery is straightforward but requires a bit of soldering. A much better method is to mount a battery holder instead. That way the next time you need to change battery, you can do it in 10 seconds! [after you have opened the case that is]

I had seen holders for the 1/2 AA batteries before, but it was not until MKL (shmups forum) showed me the Keystone holders with retainers that things became interesting. The retainers prevent the battery from being dislodged!

Parts

• Keystone battery holder (Mouser part #534-108)
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• Keystone battery holder retainer (Mouser part #534-108A)
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• One 3.6V Lithium battery, size 1/2 AA (Elfa part #69-282-12)

Equipment

• Soldering iron and solder. I use an ungrounded soldering iron to prevent any current drain to ground.
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• Desoldering wick and/or desoldering pump
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• Torx 20 security bit to open the CPS2 B-Board
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• Wire cutters
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• Tweezers
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• A drill bit of 1.5 millimeter (Must not be larger)
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• Paper cutting knife
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Disclaimer

I take no responsibility whatsoever for any damage you might cause to your hardware, yourself or your surroundings when attempting this project. Lithium is a hazardous substance and must be treated with respect. Furthermore I do not perform this service.

Procedure

Preparation

Time is of the essence here so prepare and lay out everything you need, before you start the procedure.

Open the CPS2 B-Board using the Torx 20 security bit. Remove the PCB and put it down on an antistatic flat surface.

Look at the Keystone battery holder. There is a small alignment tap underneath, near the + terminal. Remove it with the paper knife so the surface becomes level.

Make sure the drill and drill bit is ready.

Note:
I do not use a helper battery because I can perform this procedure in around 6 minutes. Normally the board will survive without a battery for at least 40 minutes but this varies. If you are unsure about your ability to perform this procedure within the time limit, I strongly advise you to use a helper battery.

Action

• Make a note of where + & - is on the existing battery.

  

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• Remove the existing battery by cutting the wires. Dispose of it in an appropriate manner.

  

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• Turn the board around and use the solder wick to suck away as much solder from the solder pads as possible. Hold the remains of the battery leg with the tweezers, touch the soldering iron to the solder and gently lift up the leg. Use the solder wick to clean up all excess solder. Use the desoldering pump if necessary to open the terminal holes.

  

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• The terminals of the Keystone battery holder are a bit wider than the existing holes so the existing holes have to be expanded slightly. Use the 1.5 mm drill bit and gently widen the holes. This must be done from the solder side of the PCB to avoid destroying the solder pad.

  

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• Insert the new battery holder, making sure you get the polarity right. Solder the terminals.

  

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• Insert the battery making sure you get the polarity right.

  

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• Mount the retainer on top of the battery holder.

  

  Note:
  You might need to shave of a small bit of plastic to make the battery retainer align correctly. There is a small SMD device (D5) just in front of the + terminal which will sometimes block the side of the lid. I use the paper cutting knife to shave off a small corner.
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• Label the cart with the battery change date. Relax with the knowledge that next time, all you have to do is insert a 1/2 AA battery.

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