Chosen Solution
So I’ve run into a problem. I was dismantling some in-ear headphones for a project and the first one worked out fine but the second has an issue. There are 4 terminals on the board. All but the bottom right one (in the images) have continuity with each other in the working driver. The driver that is having trouble has lost continuity with the bottom right terminal. I didn’t treat it any differently than the first one but something must have happened. The only thing that makes any sense to me is perhaps I got it too hot when desoldering the terminal. If this is the case, is there any way to fix it? Any suggestions as to how to troubleshoot any further? If anyone has an idea about how I might salvage this, I would greatly appreciate it. Interior of not working driver: https://ibb.co/c0QmKm Exterior of not working driver: https://ibb.co/mEQWkR Wiring of the working driver: https://ibb.co/mvDj5R Please note these aren’t actually Apple headphones but from what I’ve seen of the internals of the Apple ones, these are similar. Thanks in advance :)
Your question seems to contradict itself regarding the bottom right pad. However, 2 of the pads, as you’ll see, are for soldering the earphone lead to (let’s call them A and D), and each of these is connected by printed circuit tracks to one of the remaining two (call them B and C, A connected to B and D connected to C). The two ends of the voice coil are soldered to B and C. You may have difficulty seeing this as the voicecoil is made up of very fine wire. The only way you could have just one pad with no connectivity to any of the others is if one of the printed circuit tracks were broken. That doesn’t seem likely, though it’s just possible you broke the track in unsoldering the earphone wire. In that case you should be able to bridge the break with solder. More likely is that the voicecoil wire is broken. This would show up by continuity between A and B and between C and D, but none between A or B and C or D. This would probably be very difficult to fix. If you have around 30 ohms between B and C your voicecoil is good.
