My 40 inch samsung lcd has sound but no picture from time to time

SOURCE: Samsung LE40R51B no picture but turns on

i have the same problem i was told by a repairman that samsungs are known for bad psu. and that its expensive to repair

SOURCE: Samsung 40 inch LCD LNS4092D No Picture

I had a very similar problem, TV was 1 day old! Samsung engineer came out and replaced the motherboard - all sorted now.

SOURCE: my samsung 40

This tv has issues with 4 capacitors. These caps can be replaced for about $10. They are located at the top right corner of the power supply. They will read 10v,1000uF. I had the same problem, then I replaced them wit 16v,1000uF capacitors. And presto tv!

SOURCE: Samsung LCD 40 inch LNT4061

Howdy,
It sounds like you have a Power Supply Board problem. The PSB is the center Board (towards left) after you remove the back off the TV. Remove Board from TV with the 6-7 screws. Replace capacitors CM852 & CM853; 2200ufd 25volts.

Thanks for using FIXYA, big IRISH.

SOURCE: 3 year old Samsung 40 inch LCD TV will not turn on

The problem is 4 capacitors on the power supply board. Just had mine done under warranty. They (Sears) replaced the whole power board but you can get larger capacitors and just replace those for alot cheaper if not under warranty.