tx-p46gt30e power supply with buzzing sound.

[bachir2004]

i have this set that switches on,with a buzzing sound coming from the ac
power supply no image not even a glow,following a training
manual to switch the power supply with no load,it switches on fine
(with no buzzing ).changing the 2 power supplies leaves it with the same behavior.
Attached some photos of the set and measurements.Can
someone please help to find the problem.
measurements(I have let the set on for approximatively 10 to 15 min):
SC2=215V
C631=111V
C632=111V
TP126=0V
TP82=15.54V
TP98=1.13V
TPVAD=71V
------------
TPVSUS=215V
P15V=15.5V
P5V=5V
TPVE=164.6V
VEREF1=2.43V
VEREF2=2.43V

[tvtimmy]

Re: tx-p46gt30e power supply with buzzing sound.

Check if some of the 7 SC board mounting screws are loose . Then test for a short on the connector. Unplug tv before testing anything for 10 minutes.

[bachir2004]

Re: tx-p46gt30e power supply with buzzing sound.

thanks for your reply.the screws were the first thing i inspected.they are thightened.i can`t see any short in SC or SS board.also inspected C1 and C2 on the caps have 55v.

[tvtimmy]

Re: tx-p46gt30e power supply with buzzing sound.

Check the buffer boards for a short.

[bachir2004]

Re: tx-p46gt30e power supply with buzzing sound.

checked the buffer boards for short with reference to VFG;they are not shorted.Isolating the SC board (disconnect SU and SD and using jig) the buzzing still present.Till thr only thing i noticed is the resiistors marked in the photo are hotter than the other parts (after disconnecting the power,of course)

[bachir2004]

Re: tx-p46gt30e power supply with buzzing sound.

Iam just wondering,could it be the panel?I will go ahead and change the two bridge rectifiers under the heatsink in P2.let`s see!!

[R_J]

Re: tx-p46gt30e power supply with buzzing sound.

Try supplying a video source, does the buzzing sound change as the video signal changes, Does the sound seem to be coming from the panel? A panel that has lost it's gas can buzz.

[bachir2004]

Re: tx-p46gt30e power supply with buzzing sound.

many thanks R J for your help.in the photo you can see where the buzzing comes from.is isolaating the buffers good enough to know if the panel is good?

[R_J]

Re: tx-p46gt30e power supply with buzzing sound.

I have had older panels that lost there gas and the sound was more of a growlling/buzzing sound, but you could tell it was coming from the panel. I don't believe that board has anything to do with the panel drive, it is part of the power supply.

[bachir2004]

Re: tx-p46gt30e power supply with buzzing sound.

ok!I will check again and see what to do next.at least I would have a working SC board.thank you so much.

[R_J]

Re: tx-p46gt30e power supply with buzzing sound.

I looked at the board you have pictured in post #8 and the buzzing is coming from the heatsink for the two bridge rectifiers, so I doubt that is a problem.
I would check for shorted igbt on the Sc and SS boards

[tvtimmy]

Re: tx-p46gt30e power supply with buzzing sound.

Check these 2 parts. I had one that had a bad one on it,but don't remember which one it was.

[bachir2004]

Re: tx-p46gt30e power supply with buzzing sound.

THANKS FOR YOUR REPLIES,I AM A LITTLE BUSY RIGHT NOW.I WILL SEE THAT LATER.JUST TO LET YOU KNOW,BOUGHT THREE SETS P42VT30 ORIGINALLY WITH THE USUAL 7 BLINKS,REPAIRED, IT IS UP AND RUNNING FINE, SECOND SET IS P42ST30E SAME FAULT,ALSO UP AND RUNNING,IT HAS A THIN BLACK HORIZONTAL LINE,STILL DO NOT KNOW IF IT IS A BUFFER OR PDP PROBLEM,BUT THE THIRD ONE(P46XT30) YOU KNOW THE PROBLEM.JUST FOR INFORMATION FOR ANYONE WITH THE PROBLEM OF SEVEN BLINKS,TNPA5330,PARTS REPLACED:Q421,Q422,Q423(RJP30H2A0),Q401 Q402,Q403(30F131),and the famous ic502,q531.i hope it will help someone.will be back to the third one when i have time.i know my english is not good but bear with,i`m still learning