Well, I have the TXP-2670WH and I had the firmware upgrade done last year around December to fix my QAM tuner to get it working. Fast forward to 3 weeks ago, my TV broke and I called Samsung and they extended my warranty and had it fixed under warranty which the local center basically changed the whole board inside. I got back my TV and now I must have some newer firmware on this board that not only does not have a functioning QAM tuner any more, it also removed any mention of the QAM tuner in the menus like when going under Cable it asks if your cable is QAM capable, not there anymore.
I called Samsung and finally after tracking my original request for the QAM to be fixed sent the repair order to the local facility here who is telling me they cannot order that firmware because its no longer available. I call back Samsung and I got left on hold too long and I had to get off the phone on friday cause of Shabbat (Jewish Holiday) and was left in the limbo. I was in the process of explaining a new guy the situation showing him the previous fix plus that my documentation in the manual does show the QAM tuner as being a feature and that if I dont get the feature restored, I want either my money for my TV as that was the only reason I had originally got the TV because I dont have good reception for HDTV OTA, or they send me out a T-451 STB tuner which has a QAM tuner. I gotta call back monday to see whats up. I really hope they track down this firmware and get permission to send to me instead of having a repair guy come out and do the upgrade and restore my beloved QAM tuner.