K750i headset - 3.5mm jack mod

Hi there, I thought a few of you may be interested to see the adaptation that I have made to the hands free head set that comes with the k750i. I have had the handset for a few weeks now and have always been planning to do this mod. I got round to it this weekend and took a few pics along the way to show you all. Incidently all the pics here were taken with the k750i too!!

My previous phone was a Nokia 6230 and I have been using a modified headset with that for a long time with great results.
I originally bought a set of Sony MDR-EX71 earphones to use with this. These earphones come with a short lead and an extension, designed so that you can use them with a Sony in-line remote control. The 3.5mm socket from the extension was cut off and added to the Nokia headset as below...

This same 3.5mm stereo socket is to be moved onto the Sony Ericsson headset. To do this you will need to unclip the microphone part of the headset...

This comes apart relatively easily by carefully running your fingernail along the longer side and prying apart. The circuit board inside looks like the pic below. Here the right earphone has already been unsoldered from the board...

The left longer earphone could simply be removed by cutting the wire close to where it enters the casing with a sharp knife. I actually wanted to shorten the lead a little so I removed all the connections from the board...

The wires inside the headset lead are :

Copper : Earphone ground (-ve)
Red : Earphone right side (+ve)
Green : Earphone left side (+ve)
Black : Microphone ground (-ve)
White : Microphone (+ve)

This shows the wires re-attached to the board and the 3.5mm socket also attached. The right side positive goes to the bottom connection on the right of the board. The ground goes to the top right connection on the board. The left side positive (green) attaches straight to the wire from the headset as there is no track for this on the board and this originally went straight out again to the left earphone. The connection of this wire is insulated with a little tape...

After a short test to ensure all the sound is getting through ok and all connections are secure the casing is clipped back into place...

And there you have it. Completed in next to no time and I can now maximise the Mp3 capabilities of these phone with much improved earphones. The 3.5mm jack also now means I can use this phone with any earphones or even patch it into any stereo system!!

Hope this has inspired some of you to do the same! Who needs to wait for the W800i


Source : www.howardforums.com