ps-50q97hd problem-screen turns blank

[charlierfc]

Hi all, First of all thanks for reading. I have the above plasma tv, it turns on and the screen picture is fine and sound is fine. After a random period of time the screen goes blank and just the sound remains.I opened the tv and saw no bad looking caps ect. i tested the power going to the boards on the sticker it states the vs should be 207V on 1 side i have 204V on the other i have 208V iv tried adjusting the vs output but i cant get it to 207V on both sides. Iv replaced a few caps anyway even though they read ok in the cap tester but i have no esr reader. Does anybody have any previous with this? iv seen many on google with no picture but sound or constant click but none with this fault.
Thanks in advance.

[tom66]

Re: ps-50q97hd problem-screen turns blank

When the fault occurs is the screen still glowing? Does the Vs drop out? 204/208V is OK for this panel.

[charlierfc]

Re: ps-50q97hd problem-screen turns blank

Hi Tom, Thanks for reply. Im waiting with the cover off for it to cut off so i can get readings.
I took readings from the vs and va test points with all disconnected
vs= 204 v
va= 68 v

Weird thing, When i put my probe on the vs test point the transformer near it seemed to make a sort of buzzing noise. Im wondering if maybe a dry joint or would this be normal?

[tom66]

Re: ps-50q97hd problem-screen turns blank

These sets are well known to have cold joint issues, it wouldn't surprise me, around the main heatsinked power transistors.

[charlierfc]

Re: ps-50q97hd problem-screen turns blank

Hi, I went over the joints im still waiting on the screen going blank to do further tests. Question, with the back cover off the y sus makes quite a buzz, also the transformer i recently resoldered seems to be making a buzzing sort or pulse noise. would this be normal?

Im thinking it is the psu? as the tv comes on normal yet after some time the power must fall cutting out the picture?

typcal....when i want the tv to go blank, it wont!

[tom66]

Re: ps-50q97hd problem-screen turns blank

Buzzing is normal. They are switching large currents at high frequencies.

[charlierfc]

Re: ps-50q97hd problem-screen turns blank

Hi again, tv pic went and the reaadings remain the same, although when i came back to tv seen screen was off i tested it had stand by reading, i pressed it on and the screen remained blank with the normal readings, perhaps the tv timed itself off with no input but the tv still had no pic when turned on...

[charlierfc]

Re: ps-50q97hd problem-screen turns blank

iv reset the tv with the service menu, hey never know. info-menu-mute-power. reaso i done this was because the 3rd hdmi didnt seem to work, does now, im checking the vs power seems steady though it always was as far as i know.
i saw a vid on youtube saying som fets fail overloading the chips on the buffer board.
Im wondering if one has failed and the buffer board is cutting out due to over heat?
tv been on 1 hour so far, screen remains ok