About 8 months ago I bought a BB 7290 off of ebay. Worked grate for about a month and then no sound. Ring tone works, vibe works, mic works. Everything but the speaker to listen during a conversation. I even plugged an ear bud into it and at full volume all I get is a hum. I reinstalled the newest software and the problem is still there. I also am usting two different sim chips (not at the same time) Airvoice wireless and Att's Go phone.

Wirelessly posted (8800: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0) BlackBerry8310/4.2.2 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)

Obviously it sounds like a hardware issue and short of replacing a speaker, I don't know what else. You've loaded the OS fresh and pulled the battery to reboot the device, if not, try that.

Wirelessly posted (BlackBerry8800/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/100)

Speaker may have come unseated try taking it apart and repositioning the speaker

The headphone jack needs to be replaced. Very easy but you need a soldering iron. Get the parts on eBay. For spare parts you can strip them from any 62x0 or 72x0 units. If you don't want to deal with it go to bbrepairshop or if you are in NYC let me know.