EDIT: see post below after reading this — this approach actually does seem to have a substantial positive effect, but I missed out one of the contacts in my first attempt.
My second approach was based on the assumption that the sprung metal connectors in my headphone socket weren’t gripping the headphone plug tightly enough. I thought perhaps I could lever them out a little for a tighter grip.
This has helped: I used to lose both channels randomly, but now the socket appears to have a steel grip on
the right channel both channels — however I still lose left channel connectivity almost all the time.
It should go without saying that any modification to your phone will void your warranty.
So, I took out my phone’s top module (iFixit’s Fairphone 2 Teardown is an excellent resource, but note also the video in step 4 of their Display Assembly Replacement video — gave me much more confidence taking the display off). The top module is easily dismantled with a Torx screwdriver; after opening it, you can disconnect the PCB by gently levering out the ribbon connector.
At this point a problem becomes apparent: there’s no external access to some of the contacts in the headphone socket, particularly the two which grip the middle of the plug, carrying the right channel. I was able to lever in both the tip (left) contact and the base (ground) contact from outside the socket, but was at a loss with the remaining pair. Eventually (very frustrated by audio disconnects) I decided to drill out access holes for them. This was pretty scary, but didn’t go too badly in the end.
This is a tricky modification which requires delicacy and could do all kinds of harm to the parts affected: proceed with care.
Using a 1mm hand drill to create the pilot hole, followed by a 1.5mm drill, I created two holes in the socket to allow access to the middle pair of contacts. I initially marked the hole locations with a spike, but was reluctant to use much pressure so am not sure that that helped. Here’s the part, clamped delicately and wrapped in several layers of tissue, job completed:
The left hole is perfect; I was being very careful on my first try. Got overconfident and on the second try I drilled out of the socket a bit. Just go extremely slowly, apply the bare minimum of pressure, check your work every turn or two of the drill, etc. It is possible that 1mm holes alone would have done the job, but 1.5mm is certainly enough. You can see the two contacts, particularly the one through the right hole, and it’s trivial to stick a sewing needle in to lever them out a bit.
Needle, 1.5mm drill bit, 1mm drill bit, finished part.
As noted above, this has helped a lot, but hasn’t completely solved the problem: all I suffer from now is
left channel (tip contact); I may try opening the phone up again to tighten that further, but I think the problem may be insoluble since the tip connector only seems to have a contact on one side some rotational dropout.
Any other suggestions would be most welcome.