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Old 11-26-2021, 04:33 AM   #2
Ierwin
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Join Date: Jul 2017
City & State: Braunschweig
My Country: Germany
I'm a: Knowledge Seeker
Posts: 57
Default Re: Panasonic TX-P50STW50 Power Supply no 5V (was clicking)

I made some progress yesterday so I want to give an update.
A little breakthrough was made when I finally flipped to page 2 of the datasheet of the IC 34A65 (IC200 "STBY Control").
When I saw the example circuit I finally realized why I had been tracing in circles all across the noard for hours and hours.
The Standby Cotrol IC is driven by high voltage!
So basically the rectified main goes right into this IC over some resistors.
Once I understoof that I quickly found that one of the Resistors (R224, 2.2Ohm 2W) had failed. I have no Idea how since it shows no sign of burn or whatsoever, but it has unlimited resistance so its definetly gone.

I replaced the Resistor and suddenly everything came to live.
5V on the mainboard connector as well (YEAH!)

I was at my parents place and only had the Powerboard with me, so I once again connected 5V to Panel_Main_On, STB5V_ON and F_STB_ON using 1KOhm Resistors. After some initial Clicking and Clacking the relay just made a single "Click" when I connected main.
I think at that point the Powerboard was actually fully working and hat it been inside the TV I think it would have started.

But I had to get the board back home first. And back here its stupid thing doesnt want to play along anymore.
No 5V on the connector.
IC501 (linear voltage regulator) is getting 5.5V on the input side but does not output anything.
Could it be gone? Could it have been slowly failing all this time? Or maybe there is a short that pulls down the output voltage? Is 5.5V even enough for the voltage regulator to properly work or should I be looking in front of it?
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