Dear all,

Continuing on from this thread:
https://www.reddit.com/r/sony/comments/igdyxo/fixed_wh1000xm3_power_button_not_turning_it_on/

This being a known hardware issue with the WH-1000XM3 headphones. All functionality is fine, except the power button has issues. When the left headphone is hit/banged, occasionally it switches back on. I bought the device 4 years ago, so out of warranty.

I opened up my device, and found similar reported issues with the mainboard. The third pad from the right had significant corrosion products (black residue) and most of the pads were covered in a sticky residue. I would guess it is unwashed flux from the manufacturing process. I guess that 3rd and 4th pad from the right connect to the power button (I did not verify). When pressed with a screw driver, the corroded pad, the device was functional again.

Repair process:

1. removal of all corrosion with a toothpick
2. cleaned up all the flux residue with a soft brush and iso-propanol
3. re-soldered all the pads (just heat application)
4. dried everything with compressed air

My analysis:

• Pad corrosion, causing bad connection (high moisture environment due to the headphone being in contact with skin for long periods of time; I used them on long-haul flights).
• This same pads of the power button is at positive rail ( 5V or whatever it is) and the poor board cleaning during manufacturing is causing a conductive current leakage path, which eventually shorts, causing the buttons to malfunction.
• Cleaning off the conductive/contaminated residue removes current leakage paths, and resoldering the wires fixes the poor connection.

Now working fine again.

Good luck, let me know if you have any questions.

(Expertise: I am an engineer).

Black residue around pads is some sort of corrosion.