I have sound but my

Not enough input (info) or u using cable connection or av, if av could be the signal not going in,
Bad convegence so goes into protection,
Bad vertiacal so unit goes into protection.
Bad high voltage block so no voltage to crt's
Blowed Horz transistor, so no difflection.
If seen some RCA with this problem deppending on your model..
If seen some mitsubitchi with bad ic's but dont' know your brand.
If seen sony with shudown defflection for burt resistor in power supply but can't tell no model.

You see I can gess all day but without the info, well I could be talking of a monator.

Regards

What About Bob

THIS IS A LCD FLAT PANEL T.V. IF YOU HAVE SOUND AND NO PICTURE, IT IS PROBABLY THE MAIN BOARD.
DO YOU HAVE ON SCREEN DISPLAY ?
DON.

(Bradyjr4) sounds like you could have one of two different problems . Possible bad inverter module that regulates the picture for your display panel or problems in thr power supply . Without a meter or knowledge of how the set works this could be tricky to fix . But one of two would be your problem . For the (Guest) it sounds like a bad power supply board and your tv is going into shut down . You would want to confirm the secondary voltages are present before turn on to confirm this board is bad .