I had the above phone returned to me after selling it on eBay. On sending the phone to the auction winner all sound worked fine, however, the purchasor plugged in some earphones and on removal the phone remained mute. No sound on boot, ringtones or anything – though sound worked through the earplugs with no problem. Plugging, unplugging with numerous reboots did nothing. So I took the phone back and refunded them, it was the only honest option.
Looking on t’Internet it seemed to be a hardware rather than software problem i.e. people were reporting that the 3.5mm headphone jack that the earplugs connect into seemed to be ‘stuck’ into thinking that earphones were plugged in even when not. This must then send a hardware signal to the Phone Operating System which disables the normal speaker.
I didn’t really want to try and resolder the jack (not my forte) so I used the trusty mechansism that my wife and I applied to her water-damaged iPhone4 to bring it back to life – cotton buds and surgical spirtr. I dipped the buds in surgical spirit and cleaned the headphone jack on the phone. A few bits of detritus emerged so I continued until nothing else came out. After letting it dry for a couple of minutes I powered off/on the phone and the speakers sprang back to life. Lovely.