After a few questions on the message board, matt(v) wrote up this "never to be seen again guide to PSX control hacking."  Little did he know that I'd post it permanently :)

Notes:

1. All descriptions and instructions in this guide are for a genuine Sony gamepad, standard version.  The principle would be the same for cheap imitations, but the Sony pad was all I had to work with so that is what I used.

1. You will need some soldering skills to pull this off successfully, if you don't already know how to use an iron don't expect to find out here.

1. Yes i KNOW that the controller has a common ground trace, but this explanation is nice and easy to understand and uses simple concepts that anyone can understand. you want a guide for wiring up the controls using a common ground? your write it.

1. I assume you already have some knowledge about arcade controls, how a microswitch needs to be connected for NO (normally open) mode etc.

1. I can't spell (saint's note - I grabbed a dictionary :) )

Theory

There are 8 buttons and 4 directions on a Sony gamepad.  The control is actually 8 directional, as diagonals are achieved by holding down two adjacent directions.  This is exactly the same way that diagonals are achieved on 8-way arcade sticks.  Four of the buttons are arranged in the Circle, Square, Triangle, Cross pattern that we are all so familiar with from TV adverts.  The other four are on the front of the controller in a sort of "trigger" configuration, two triggers for each forefinger.

Every time any button or direction is pushed on the controller a piece of conductive material connects the traces beneath it and a circuit is formed. It should be trivial then to simply replace the conductive material with a microswitch which completes the circuit in exactly the same way whenever it is closed.

A playstation controller actually has a 'common ground' for all buttons but I am choosing to ignore that for now, it means more soldering but it makes the whole process much easier to understand.

Practice

Step one

Remove the screws that are holding the gamepad together.  Depending on the revision of the controller there will be either 6 or 8 - they are 2.5mm philips type screws so any small philips screwdriver should do nicely.  Take off the plastic case of the controller (comes off in two halves) and keep for later.  Pull out all the buttons and directional pad along with the rubber template underneath them.  You can keep these for repairing other control pads that break or throw them away, they are not needed for this project.  You should be left with one large PCB with the main cable coming off it (the one that plugs into the
playstation) and two small PCB's that are where the trigger buttons used to be.

Step Two
Wiring up the joystick

Find the two rubber pads that correspond to "up" on the PCB (it's labeled as up for goodness sake!) and scratch the rubber off them until you reach copper (you may have to scratch quite a lot off).  Solder one piece of wire to each bit of exposed copper, making sure they do not touch and that you have not made any solder bridges.  Connect these two wires to the switch that corresponds to "up" on your arcade joystick.

Find the two rubber pads that correspond to "down" on the PCB and scratch off enough black rubber to expose some copper for each pad.  Solder a piece of wire to each of the copper traces you just exposed and connect these two wires to the "down" direction of your arcade joystick

Repeat this process with the left and right directions.  It is vitally important that you don't burn the trace on the PCB while soldering and that you don't create any short circuits with solder.

At this point it might pay to plug what is left of your controller into the playstation and check that the directions are working properly.

Step 3
Wiring up the first 4 buttons

These are the circle, square, triangle, cross buttons. They should be labeled on the PCB as SW-O (for circle). SW-X (for cross) ect.

Find the two black rubber pads that correspond to triangle, the top button. Scrape off enough black rubber to expose the copper traces for each pad (you will have to scrape off most of the rubber to find the trace).  Solder one wire to each trace then connect these wires to the arcade button you want to be "triangle."

Find the two black rubber pads that Correspond to Circle, the left button, Scrape off enough black rubber to expose the copper traces for each pad, solder a wire to each pad and connect to the arcade button you want to be "circle."

Do the same for cross and square.

Remember the triggers were controlled by those tiny PCB's attached to the main one? Take the right one of those and look at it. there will be 2 black rubber pads labeled R1 and 2 black rubber pads labeled R2.

Find the R1 pads and expose some copper for each of them.  Solder a wire to each of these and attach these wires to the arcade button you want to be the right top trigger button.

Find the R2 pads and expose some copper for each of them.  Solder a wire to each of these and attach these wires to the arcade button you want to be the right bottom trigger button.

Now look at the Left tiny PCB, there will be 2 black rubber pads labeled L1 and 2 black rubber pads labeled L2.  Repeat the same process as for the right trigger buttons

Looking the the main PCB again you should find a pair of black rubber pads labeled "start" and a pair of pads labeled "select".  Expose some copper on the two start pads, solder a wire to each of them and attach these two wires to the arcade button you wish to be start.

Expose some copper on the two select pads, solder a wire to each of them and attach these two wires to the arcade button you wish to be select.

I suggest you try and fit the PCB back inside the plastic case you took off in step one. Run each pair wires out of the hole in the top where their original button was and you won't get confused later.  Put the whole thing back together and use a couple of the screws you saved in step one to keep it that way.

Plug your controller back into your playstation and out to your arcade controls. Chances are that some of the directions will be the opposite of what they should be but that's easy to fix. Check that the diagonals work, you MUST have an eight way arcade stick.

Kick some poor bastards behind (saint's replacement) at a fighting game.

Final notes

You may want to CAREFULLY drill a hole in each trace to be soldered and pass the wire through from the back, this makes it easy to solder and makes the join much stronger. Be careful that you don't destroy the circuit doing this and that the trace doesn't lift.

Anything to add?  Any obvious errors?  Anything I need to clarify?  Just let me know house@sinesurf.co.nz