So if you try to turn it on, does it do anything, or does it click on for a couple of seconds, then click back off?
Then try to turn it on, and then when it clicks off, go up to the front panel and press the INPUT and MENU buttons together for at least 6 seconds.
This will cause the front panel LED to flash a sequence of two numbers. For instance, if the set is working correctly with no problems, the LED would flash once, then twice, then pause, then repeat a few times. Find out what yours does and get back to me.
Oh. Well, I'm afraid it's having a problem with the stand-by power supply. The good news is that this may be a simple problem. If you have electronics experience, you might be able to fix this yourself, but it sounds like you'll need to hire a tech.
By the way, you're sure it's plugged into the power, correct? You might try unplugging it for 30 seconds, and then plug it back in, and see if it works. If it doesn't, it's definitely broke.
The standby power supply is a part of the main power supply and is on the Main Board, which is on the right side when viewed from the rear.
First check the fuse, it's near where the power cord comes in.
If that's good, check for 12 volts DC at TP12VS. If that's not there, you're going to have to pull that board out and troubleshoot the primary (hot side) of the power supply. Look for a broken solder connection on that side of the power supply, because it's rare that this set has major power supply problems.
You might consider contacting PTS Corp. and seeing if they can rebuild the board for you.