Olevia 26" hdtv - sound, no picture

If this is an LCD TV, it's probably the backilight inverter that's gone bad. Without the backlight, the display works but you can't see it. It may be possible to repair the set by replacing the inverter. Several sites sell boards removed from other sets (the TV version of an auto junkyard). One of them is shopjimmy.com. You can also try a Google search for "replacement inverter" for your specific TV model.

If you can find the replacement board, it's not difficult to change. It's a matter of removing the back of the set, unplugging the cables from the old part and connecting the new one in its place. Rather than relying on the cable tech (they normally don't know anything about TVs beyond where to hook up the cable), you might want to get an estimate from a TV technician if you don't feel you can attempt the repair yourself.

its a service mode only.