Here's the process I went through to replace the stick, a learning process for me so hopefully it will be of use to others:
- remove the SD card and stylus, and pull open the SD card, USB and charger covers.
- remove the 4 black screws on the rear case
- prise the rear case off - I started at the SD card slot, using a small flat-blade screwdriver slid between the rear case and the grey plastic surround where the shoulder buttons are. Once you can get one area to pop out slightly, work around the rear panel using the screwdriver gently prising it open.
- open the rear panel gently
- there are 5 small cables to the PCB - 2 for speakers, these can be unclipped. 1 for battery, also unclips. 2 are soldered on and lead to small round metal things in the rear case (for vibrations or tilt sensing perhaps??) - use a flat blade screwdriver under these round metal things at the point where the wires are soldered on - you can slide it under the flat plate that the wires are connected to and gently prise the metal cylinder upwards and out. Mine had some glue or sticky stuff on but came out easily enough.
- rear case should now be free.
- undo the 4 silver screws that hold the PCB down.
- gently lift the PCB and you can see how the ribbon cable to the screen unfolds - you can stand the PCB upright along the bottom edge of the case without flexing the ribbon too much. Try to keep the PCB parallel to the case to keep the ribbon straight at all times and not twist it around.
- remove the plastic thumbstick.
- now you need to desolder the joystick - I used a solder remover to suck the melted solder off each pin at a time, which worked for all apart from 2 pins. For those the solder would not melt - I gently prised the joystick off from the other side of the board, snapping off those 2 pins. I then used a Dremel with a pointed die grinder to flatten those 2 pins on the screen side of the PCB, then bored a small hole into the old solder so that the legs on the new joystick could poke into it.
- insert the new joystick, will only fit 1 way around. I had to cut down the 2 legs that matched the solder holes I had bored, until the joystick sat flat on the PCB and the 2 plastic nubs on the underside of the stick poke through the 2 holes in the PCB. I had about 0.5mm gap under the joystick, couldn't get it completely flat on the PCB.
- resolder the pins that are poking through the PCB
- for the 2 problem pins that were pressed into the old solder holes I just left them unsoldered as they're a tight fit, but you could resolder them on the joystick side of the PCB I suppose.
- place the plastic thumbstick on the new joystick - it fits on only 1 way around as the stick has a step in it.
- make sure the A,B,X,Y buttons are still in place with the white rubber thingy pressed into them.
- put the volume and on/off sliders into the centre of their slots, then do the same with the actual sliders on the PCB so they all line up.
- replace the PCB into the top case, carefully folding the ribbon cable. It took me a few tries to get it into place without the thumbstick falling off, also it needs to slide under the flexible rubber connector that holds the SD card cover on.
- make sure the volume and power sliders are moving their sliders on the PCB
- make sure the new thumbstick is free to move, mine slid off the stick a bit twice and rotated, so it was too tight against the upper case and would not self-centre. I twisted it gently around until it reseated on the step on the joystick, then it moved normally. A tiny blob of general purpose grease on the joystick would probably hold the thumbstick on quite nicely I would think,but I didn't have any around.
- at this point I carefully reconnected just the battery plug and tested the console by holding it tightly together and then turning it enough to see the screen, make sure the new stick and the all the buttons work.
- replace the 4 silver screws
- reconnect the 2 speakers and the battery
- replace the 2 silver cylinder things into the rear case
- refit the rear case and the 4 black screws
