Lost audio from the 3GS earphone 3.5mm jack, and it won't cut off the speaker when earphone inserted.
Part arrived half-way around the world in 2 days. Dismantling the phone required some delicate handywork.
Process took 2 hours, mostly disassembly and fitting the new part.
Replacing the earphone circuitry was a little tricky, especially when transferring the switches to the new location. Used a soldering iron to melt the two plastic prongs on the new mute button switch.
Earphone now works as new. Volume buttons and Power switch also firmer with a more clicky feel to them. Nice!
Study the steps provided on iFixit and take note of the screw locations, and keep them organized after unscrewed.
Did not find the actual steps to transfer the switches, so had to improvise going along. Mostly just carefully removing the stickers from the old circuitry.
Put a small double-sided tape under the new earphone jack to keep the circuit stuck to it.
The original battery is a bit finicky when removing, do not bend it during removal or it might bulge slightly and push up the circuit board afterwards.
Overall fairly straightforward, you too can DIY ! Fixed my 4 year old phone. Thanks iFixit.