Tv turns on for 5 seconds then switches itself off and the stand by light flashes

if you take the cover off, then take a look at the capacitors.
check if any have bump ..

These blinks (flashes) are fault indication. By the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit stage inside the TV. Count the blinks occur at one time switch ON, carefully. Do it once again, and make sure about the number of blinks. If the flashes are continious, non-stop, the main system control IC should be suspected. If you wish to get more details, check the site linked here. It has blinking codes detail to many brand TVs. Pull up older posts. http://electronicshelponline.blogspot.com/ Check the site in 'Mosaic' view. It will make search easy.

I finally managed to solve this problem by unplugging everything - scarts - HDD cables - power etc and left it for an hour. When I turned it back on again the problem had sorted itself out.

the four flash is a signal, it means either faulty power supply or deflection circuit trouble.

If you bought it brand new from a dealer, I would take it back or have them come out and look at it. Less than a month old, it is still under the 1 year MFG warranty or the very best a 30 day one.

t does sound like a bulb problem, either its over heating and shutting off to protect itself, or its already shot. Give a TV repair shop a call and see if they can give you an approximate price, then decide to ditch or repair it.

turn tv on picture comes up 2to3 seconds later tv blacks out then stand by red light flashes 4 times in a row repeatedly..can not turn on or off when stand by light starts flashing but before tv blacks out you can turn tv on and off repeatedly and picture and sound work.You have to unplug power cord for 30 seconds after stand by light comes on to get tv to turn on.

MAGNAVOX TV ONLY. 5-10 SECONDS AFTER TURN ON AUTO TURNS OFF-NO LIGHT STAYS ON-I AM FRUSTRATED BUT IT SEEMS LIKE THE OFF ON SWITCH JUST CLICKS BACK TO OFF-ALSO DOES SAME THING BY REMOTE

The STANDBY light is flashing on the television and there is no picture or sound. Solution
The STANDBY light will flash if an issue is detected within the television. This can sometimes be resolved by simply following the steps below to reset the television.

1. Turn off the television. IMPORTANT: For a projection television that uses an internal lamp, wait 5 minutes after turning off the television to allow the lamp to cool before continuing with the following steps.
   
2. Unplug the television power cord from the electrical outlet.
3. Let the television remain without power for 60 seconds.
4. Plug the power cord back into the electrical outlet. NOTE: If the television is plugged into a power strip or surge protector, remove it from the power strip or surge protector and plug it directly into the wall outlet. If the issue is resolved, the problem is with the power strip or surge protector and not the television.
   
5. Turn on the television.

If the issue is still unresolved after following all of the troubleshooting steps, service may be required. Please note the number of times the STANDBY light flashes and relay that information to the service center.

Its the BULB people! You need to change it every 3 to 5 years! I have had my sony 55" for 6 years... I had Best Buy come out 3 years ago, changed the bulb... it worked fine. Just started flasshing and shut its self off and back on again. Time for another bulb.