I have a Magnavox 1080p HDTV. It’s a couple of years old. Now when I power it on, the picture comes on only for 2-3 seconds then goes dark. Every time. All other functions work, including sound and switching source. I have a Wii and a Verizon FiOS settop box and it has the same behavior regardless of source.
I am guessing that these TVs are so complex and tightly integrated that I have no hope of doing anything myself to fix it. I have a very rudimentary understanding of electronics and know how to use a multimeter, but I think that means I know enough to be dangerous. But I figured I could at least ask.
Does the sound go out also or just the picture?
If it’s both and the set keeps powering off it’s probably a bad power supply.
Unfortunately even if it’s only just that it’ll be cheaper to buy a new one than to get it fixed.
If you are handy with a soldering iron or have a local electronics repair shop, it may be bad capacitors and fixable for not much money. Apparently in recent years there have been a lot of bad capacitors coming onto the market from Asia.
Bad caps in the power supply would be the first thing I would investigate. When the caps go bad, the power supply cannot keep a steady voltage under load, so it works for a little bit and then fails when the voltage drops. As control-z notes, bad caps are usually easy to spot and cheap to replace. All it takes is the gumption to open up your set and attack it with a soldering iron.
Do all the sources plug in directly to the TV or are they being routed through an A/V receiver?
I had similar behavior that I tracked down to a bad HDMI cable. But for that to be be the explanation in your circumstance everything would have to be routed through the same bad cable. The only way I can think that would be possible is if everything goes through a receiver and the receiver is connected to the TV with a bad HDMI cable. Probably not what is going on but a cheap and easy fix if it is.