Recently I bought a PSOne with two Dualshock controllers, one being the Diamond Black PSX controller and the other the stock white PSOne controller. After a while the sticks started to drift on the black one, so I decided to take it apart and completely clean it. Note that this is for the model SCPH-1200 controller ONLY. the Dualshock 2 for the PS2 (SCPH-10010), the rumble-less version SCPH-10520 as well as the SCPH-110 Dualshock from the PSOne have different internal layouts.
Step 1: Disassembly
First you need to take apart the controller, which is accomplished by removing the seven screws on the bac, then pulling the back off.
Step 2: Guts
Next thing you need to do is to remove the PCB and rumble motors. This is accomplished by pulling the motors out (one has a plastic holder, don't loose it), removing a screw, unplugging the ribbon cable that comes from the conductive mat for the buttons, and pulling the PCB out. Note that there is a small plastic light tube near the screw. This directs light from the LED on the PCB to the hole for the analog indicator light. Don't loose this because it also helps hold the case together. After pulling the PCB out, you will need to pull the cable that goes to the PSX out from around the stress relief posts. Also, pull the sticks off of the PCB so they can be washed.
Step 3: More Guts
Last thing to remove before a total wash of the case is the whole button
assembly. This will pull right out of the case. Now, pull the rubber
plungers from behind the buttons and then remove the buttons. Next, pull
the L1 and R1 buttons off of their frame, as well as the rubber bits
there as well. To remove the L2 and R2 buttons from the bottom shell,
just push then from the outside and they will pop out. There is also a
small X-shaped piece (mine has one leg broken off) under the D-pad that
you want to keep. This keeps the D-Pad from going all directions at
once, so don't loose it!
Step 4: Scrub Away!
Now its time to start the actual cleaning. Take the outer casings, buttons, sticks, and the rubber plungers that go under the buttons to the nearest friendly neighborhood sink, preferably with a MESH strainer in the drain, or you could toss a dishcloth or such over the drain. You don't want one with slots because some of the parts could go through and then you would have a non-functional controller.
You want to start by rinsing all of the parts off. I used a toothbrush and Dawn soap here but any soft-bristled brush and mild detergent would work. Get some soap on your brush and start scrubbing away, paying careful attention to the edges of the case bits, insides of the button holes, and around the edges of the buttons (the bit that rubs against the case.) Dirt tends to get stuck in these areas.
After you get everything clean and rinsed, lay it all out to dry on paper towels or such.
Step 5: Cleaning the Sticks and Buttons
To clean the two analog sticks, which is why I cleaned it in the first place, spray some isopropyl alcohol into the small green boxes, there are two per stick. Then move the sticks in circles for a bit and used an office duster can to dry them out and remove any debris. This step really helped, before my right stick was drifting to the left and the dead zone was pretty wide. After cleaning the drifting stopped and the dead zone shrunk quite a bit.
Now, I decided to clean the contacts on the membrane inside the PSX, so I took a q-tip, soaked the tip in some alcohol, and wiped the pads down. Make sure you get the ones for the L and R buttons as well.
Step 6: Reassembly
Now that everything is clean and dry its time to put it back together! DFirst, start out by putting the rubber mats back into the L and R buttons. Then, put the buttons back into the case (note the X, square, triangle, and O buttons are keyed to fit.) After putting the D-pad in, put the odd little X-shaped piece in with the ball side towards the D-pad. Next, put all o0f the rubber plunget stuff in, including the ones in the L and R button frames and the start/select/analog button. Then snap the L1 and R1 buttons back into the frame, making sure they aren't upside down.
Step 7: Reassembly, Part 2
Now we want to put the internal plastic fame and the button membrane back into the controller. This is really simple and consists of lining everything up and pushing in. Next, you want to put the sticks back onto the PCB, which is done by simply pushing them onto the tiny metal sticks. Also, put the R2 and L2 buttons into the bottom case simply by dropping them in and pushing them down, the same way they came out.
Step 8: Reassembly: the Final Saga
Now that all the components are together, its time to put them all together. Start with the upper case/buttons and the PCB. First thing you need to do is put the small light tube back into its place. The angled end goes on top of the plastic fame with the screw hole fainc upwards. Then, put the cable back through the stress relief posts. See the image for how, but the cable should be bent still from sitting there a good ten or so years. Now, lay the PCB down into the case, making sure to leave the button ribbon cable exposed and not trapping it under the PCB. This might take some jiggling. Now that the PCB is in, screw it down. Carefully plug the ribbon cable back in, using the tabs on the sides to help push it in.
Now, put the right (with the controller open face down) motor back into its plastic holder if it fell out and set it into the case. There are some guide rails in the case as well as a small post that the hole in the holder goes on top of. The left rumble motor just sits in the holder molded into the case.
Finally, take the bottom cover, and while tilting it slightly forward to keep the L/R2 buttons out of the way, set the tom half of the controller down into it. Now, simply reinstall all seven screws and you are ready to test it out!
Step 9: Troubleshooting
If none of the buttons work, make sure the ribbon cable is plugged in properly.
If you have one or two buttons not working, try cleaning them again.
If the analog sticks are off, clean them again.
If any of the buttons don't work and they have nothing pushing them back up out of the case, you forgot to put one of the rubber plunger mats in.