Samsung UN55F6300 won't start & keep blinking red light 5 times. New power supply board but didn't work. So, I replaced it back with original and worked fine for a few days & now won't start again.

SOURCE: sony sxrd 60 in, won't power up--blinking red light 5 times

You need to replace your bulb. Order a replacement online---it's easy to swap and the instructions are in your manual. If you purchase one from a local dealer you will pay over $150 more!!!

SOURCE: sharp lc-22sv6u won,t power on. no green light.

Sound like the TV is in protection mode. This happens when a part goes bad inside. the TV turns OFF to protect the other parts from being damaged.
Most commonly it's a power supply related issue. A bad capacitor or transformer on the power supply board is to blame.
For a do-it-yourself fixer with electronic experience, a Service Manual is the best for trouble shooting the problem down to the bad part. Normally, you can find it over the internet for less than $20.

SOURCE: My SXRD 60

Perhaps it needs the bulb, but there is also a good possibility that the lamp fan is getting clogged and shutting down the set. This is NOT the fan you see in the back, instead, it is above the lamp, and is a small blower-type fan, that tends to clog with dust. You CAN check this, when you open the lamp door,you can see the blower wheel, and if it is all dusty, it needs to be cleaned out--but do NOT just blow it out, or you might clog the engine!! It needs to be removed, and cleaned out of the set.

But first...if the blower is not too dirty...try another lamp.

SOURCE: Samsung LN46A550 LCD power on/off

Apparently this is a known problem with flat panel TVs made a few years ago due to bad capacitors in the power supply. This same problem appeared in computer mother boards at about the same time so that the capacitors went open or shorted causing problems.There is videos on You Tube that addresses this problem see: http://www.youtube.com/watch?v=ZccykxrtX9g as a starting point and look around for other repairs

SOURCE: I have a 4 year old Sony KDF-E42A10 television -

I Have a sony 50inch grand waga rear projection tv replaced bulb earlier on in the year i cannot reset the bulb program and now power light blinks 4 times sound but no picture can you help please