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Old 11-29-2021, 03:12 PM   #5
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)

Thank you very much for looking into this.
I hope I can provide some more measurements later when I am at the board, but for now I can at least give an update from memory.
Since the 2
2Ohm resistor was replaced ic200 seems to perform well. It's getting 310Volts on the HV input and if I remember correctly is outputting 15V.
What I have done since my last post:
I disconnected the output leg of the 5v voltage regulator from the rest of the circuit.
With this connection open the regulator has 7.2V on the input and 4.6 on the output.

I suspected the regulator to be faulty and used a 78S05cv as a temporary replacement just to see what it does. This also causes the voltage on the input line of the regulator to drop and the output of this regulator is about 3,5Volts.

I suspect that either the input of the regulator is lacking Power so the voltage drops under load or a short on the output side of the 5v regulator.
Actually I think it is the first because I connected an external power supply to the 5V circuit and the circuit was pulling about 250mA (not connected to mains),which seems reasonable an not like a short.

Maybe the error is on the primary side of T200. If I remember correctly Q110 is involved there as an amplifier of the driver output of ic200. Oh by the way ic200 is a 34A65.
I had previously checked Q110 for shorts bit it seemed ok.
If you need more measurements or Pictures let me know
Ierwin is offline   Reply With Quote