iPhone dock mod

Recently I bough some iPhone docks from DealExtreme in China. At 5 Euros a piece it's quite a bargain. It can be used for charging and even has a line-out to connect speakers. The latter was the problem however. It disabled the on-board sound of the phone even if no external speakers were connected. As I wanted to use at least one of them just for charging on my night stand and probably as an alarm, this posed some kind of problem.

Fortunately a quick search found a blog post that described a simple mod to deactive the muting feature completely. That was already what I wanted, but my inner tinkerer wasn't satisfied and looked for a way that only enables the muting of the internal sound when an external speaker was connected to the line out jack.

For this a sensing jack was needed that could tell if something was inserted into it, but a quick check of some major electronics suppliers didn't bring anything up that matched the board layout. So I had a look at the existing jack and modified it. I made some photos in the process. They're not great but should bring the point accross. It's quite simple really:

First I drilled a very small hole in the jack that ends directly under the mass connector. This is the difficult part.

Then I stripped some bit off the insulation of a wire and inserted the blank end into the hole:

Afterwards I made sure that the wire was bend exactly the way that it only touched to the mass connector if a plug was actually inserted. When this worked to my liking I fixed the wire in place using some repair putty. Some simple tape would perhaps have done it, too ;-)

And finally, after the putty became hard as stone I connected the wire through a resistor to the signal pad on the board. I used a wired resistor instead of the original SMD model as it was just easier to solder this way. The original was 75k, I only had 68k and 80k here and opted for 68k, but I think anything goes really.

All of this took maybe 15 minutes, excluding the time the putty needed to dry. Put everything together again and the dock now works like you would expect :-) If you want to try it, too, have fun! But I'm not responsible if you break the jack...