Help Earpiece broken - no sound during calls

[bli]

I have a Galaxy S2 on the o2 network in the UK. Recently, the USB port was playing up so I got a replacement off eBay. The replacement worked fine. However, after replacing that part, the earpiece in the phone stopped working so I can't hear anyone during calls. I can hear them fine if I plug in headphones. I got a replacement earpiece (the part actually contains the earpiece, headphone jack, secondary mic and vibrator) and put that in but it hasn't made any difference - everything on the phone works other than the earpiece. I've tried swapping the USB board back out to the original I had (where the earpiece was still working) but I just can't get sound out of that anymore. I thought that maybe it was due to a software issue but I've also done a factory reset of everything and flashed back to 3 different stock firmwares (with stock modem) and it made no difference. I've unplugged any connectors I can see on the motherboard and given them a quick blow out then put them all back in but still no sound from the earpiece.

Does anyone have an idea how to fix this?

 

[Gearu]

Try cleaning the headphone jack with a cotton swab stick, it may think there is a plug in there when there isn't due to dirt, even though it doesn't show the headphones icon in the status bar.

 

[bli]

I tried cleaning the headphone jack and it didn't help at all. I then tried the earpiece I had bought in another S2 and it didn't work. I bought another one off eBay and it works fine. Turns out I had just been really unlucky and after breaking the original earpiece, the replacement I bought also had a broken earpiece.