Use following steps to reset channel, but I lost the sound
1. Unplug TV
2. Press Channel up and Volume up at same time, while plugging TV back in (two person job - it will pull up a service screen)
Same no sound issue happened to me; except I stopped at adjusting vertical size (unfortunately it seems horizontal cannot be set thru service mode; which was my original intent). Complete lost of sound signal processing; oddly enough speaker volume leveling did worked. (Eg, audio-in woks; so a big WTF?!) I suspect something to do with not recovering properly the data bus from muxing the volume input keys; ie, some kind of weird service/back-to-normal switch bug. I've waited for a couple of days for the damn thing to unlock itself out it (like some stubborn transistors seem to do); but to no avail. (BTW, only dif between TVs is that mine's a slightly smaller and cheaper model, a 19U-M100S; a minor branch out of the main line.) I'm afraid something did "burned out" and that the only real fix is to actually change the "defective" part. Had I known silly sh1t like that could happen, I obv would've not messed with it to begin with. It's just ridiculous, and lame. Besides being obsolete. In any case; I also think it's nowadays better to get a (full) digital one (wisely cost effective).