My 50 inch philips plasma tv wont come on. all it does when you turn on the power is that the blue light comes on like usual and you hear a relay click and then a few seconds later you hear a relay clickin on and off. does that mean the power relay is bad or is it something else?

There are a few common gotchas for all plasma TVs:

Most commonly, a sustain board overheats and burns out; sometimes that prevents the TV from powering and sometimes it does not.
Unfortunately I don't know enough about your particular model to tell in which category it falls.

Second, the power board either breaks too (sometimes as a result of a sustain defection) or filter capacitors on it dry out and prevent the board from powering on properly. This, in turn, is detected by the protection circuits on the power board itself and treated as a short circuit, thus shutting down the board to prevent further damage.

In my experience 80% of the time the problem you describe is caused by burned ZSUS board and 20% are due to defect power board.

As I said earlier when a sustain burns out it sometimes takes down the power as well. Which is to say do not presume that just one board has gone bad.

One of these days I am planning to post a DIY troubleshooting guide for plasma TVs at my site http://www.coppelltvrepair.com .

It's easier than many people think.

For example in your case I'd try to power off the ZSUS board - the one on the right side of the TV when you watch from the back - and turn it on again. If it powers on then the problem is in the ZSUS board.

In fact, there are quite a few such guides circulating around the net.

The problem ,of course, is that it takes time to understand and apply them properly.

Unless you have a lot of time to kill or a desire to enter the field of TV repairs it's usually better to just pay off a good technician.

Developing the qualities to find a good specialist is a challenge well worth the time and will pay many times in life.

The same can not be said very safely for the qualities of repairing plasma TVs :-)

I had the same problem with my 42" Plasma Philips... I was able to fix it. email me jules_richard (at) yahoo...
you have to open the back and replace two (maybe three) capacitors. I can tell you how, if you are not sure.