I have come across a few pairs of HD25 with driver faults. Sometimes it’s just a lose connection and unplugging the cable and plugging it back in seems to fix it but sometimes the fault is more serious.
(DO NOT TRY TO REPAIR OR MODIFY HEADPHONES UNLESS YOU ARE SKILLED IN THAT SORT OF THING)
First of all I had no idea how the socket worked so a bit of an investigation was in order
1) Lifting up the cover
To get the grate/cover up just stick a small flat headed screwdriver in here ….. And levered it up
2) Under the hood
The socket is covered by a plastic cap
3) Remove the cap – DANGER MAKE SURE YOU MOVE THE VOICE COIL WIRES OUT OF THE WAY FIRST ( I broke the first one it tried )
The cap had a handy tab which you can get hold of with some small pliers. Pull gently out making sure not to damage the thin wires leading to the voice coil
4) How the socket works
Turns out the socket has two coiled springs inside linked which push up against the two gold posts either side. The prongs of the HPSC connector pushes in between the coils of the springs – this means that the problem can not be caused by lose contacts inside. The most likely cause is gunk / dust getting on the connection between the spring and the gold post.
5) The fix
There three options here depending on what is causing the issue
A) Oxidisation / fluf. The most common cause is a build up of oxidisation or gunk on the spring this can be fixed by using a small flat headed screwdriver to scratch / clean the dirt off the spring this can be done sometimes by just unplugging the connector and reinserting a few times – this can ware off the layer of oxidisation and can fix the issue without having to open the cup
B) The spring can get lose and cause a gap where the connector goes – to fix this just stick a small screw driver in the gaps at the end of the spring and twist it to make the gaps at the end bigger and make the gap in the midle where the connector goes in smaller and tighter.
C) if all else fails the voice could may have a lose connection to the pillars – you can solder it directly to the spring but I would warn that is is v-tricky and likely to fail so only try as a last resort
Hay presto….. Fixed