Like when I turn it on, the power light goes from red to green, and it makes a high pitched buzzing ....

is the high pitched buzzing sound coming from the rear right of the screen if so its its the board that needs to be replaced the board no is 42sd3_zsus
A.White bernadette.mcmanaman@sky.com

If the sound seems to be coming from the right rear of the set, it could be the inverter board is arcing when trying to turn on the backlights, indicating a bad inverter baord, maybe a cracked solder connection on one of the transformers (a very common problem) This would sound like a buzzing, or a sparking sound. If it is coming from the speakers it could be a power supply problem

regarding fixing a broken plasma sreen here's my experience with a 60" Zenith Plasma. The TV did the same as your TV when powered on. It would buzz and then fail to power up. We sent it in with an estimate of 'no higher' than $3000 to fix. The repair came in at $5700! The owner of the shop guaranteed we would have no further problems. As 'they replaced virtually every module' in the TV. Two months later we are having picture quality problems. I WISH I'D OF CUT MY LOSSES AT THE FIRST PROBLEM! Hope you do better

If anyone would have paid $5700 to repair any TV they need more then they're Loses cut off. The dealer that pulled this stunt needs to be reported to the consumer fraud dept. This is totally out of line and I would have taken his ass to court.
I have been in the TV repair business for over 25 years and if I ever charged anyone even half of that I would have been under investigation by the state regulatory division and also the better business bureau. Man you should go back to that dealer or repair shop with a sharp object and start cutting off items below the waisteline.

You need to replace X-Y sustain board.

That BUZZING Noise As a last note, it’s been reported that plasma has an issue in very high altitudes where air-pressure differential can cause the sets to emit an annoying "buzzing: noise. Some manufacturers claim to have compensated for this, however, if you live in a high altitude, keep it in mind when examining sets at your local retailer.

If everyone took this last poster's experience and assumed all repairs go that way, nothing would be repaired. As for your problem, it's possible you need a power supply, but you would need someone to evaluate it first. Good luck.

try replacing the scaler module

The high pitch noise you're hearing may be the switching power supply squeeling due to a shorted output or a abnormally heavy load on one of the boards. This does not mean the panel is bad or defective although this could be the case, it is pretty easy to idntify the problem once the back is removed. Please refer service to a qualifed servicer for inspection.

Joe Weibel

It's the scaler board according to my tech. The replacement board is no longer manufactured.