Panasonic P50VT20B Plasma 12 Blinks, Power Supply or A-Board?

[Biruslapio]

Hello, I've had this TV for 3 years, 2 years ago it stopped working signaling 12 Blinks, SOUND_SOS according to the service manual.

It has no VSUS or VDAT, and P15V has 1.0V instead, the same 15V goes to A board. F15V is ok and other main voltage rails.

It seems the power supply is defective, since unplugging D20 ribbon cable that goes from D-board to SC-board makes the behavior change, the TV stays on, there's no image nor VSUS, but 15V reads 2.4V, high enough to not trip the SOS 12 blinks, so it stays on, fans do not spin but I left it 2 hours, green led lit up and didn't shut down.
There's no shorted caps, ICs or low resistance on P15V rail that I've measured.

Is there a way to test the power supply separatedly from A board?

It's late now, tomorrow I'll update with P25, P6 and P7 multimeter readings.

https://www.electronica-pt.com/esque...pf13dda-34828/ service manual link

TNPH0890 - A board
ETX2MM806MVH - P board

[Biruslapio]

Re: Panasonic P50VT20B Plasma 12 Blinks, Power Supply or A-Board?

Measured with my crap multimeter, it's reading a voltages little less than it should

Pin Number / Name / Power Switch OFF Voltage / ON voltage

P6
01 - SOUND+15V / 0V / 2.38V
02 - SOUND+15V / 0V / 2.38V
03 - P+15V / 0V / 2.38V
04 - GND
05 - GND
06 - GND
07 - F+15V / 0V / 14.02V
08 - GND
09 - F+15V / 0V / 14.02V
10 - GND
11 - GND

P7
01 - STBY+5V / 0V / 4.83V
02 - GND
03 - S0 / 0V / 0V
04 - S1 / 0V / 0V
05 - TV SUB ON / 0V / 3.06V
06 - GND
07 - PANEL_MAIN_ON / 0V / 0V
08 - STB5V_ON / 4.68V / 0.17V
09 - SOS4_PS / 0V / 0V
10 - NC
11 - GND
12 - MAIN SW1 / 0V / 4.8V
13 - NC
14 - MAIN SW2 / 4.85V / 4.8V

P25
01 - P+15V / 0V / 2.38V
02 - P+15V / 0V / 2.38V
03 - GND
04 - GND
05 - GND
06 - STB+5V / 0V / 4.83V
07 - S0 / 0V / 0V
08 - S1 / 0V / 0V
09 - PANEL_MAIN_ON / 0V / 0V
10 - SOS4_PS / 0V / 0V

There's 0V going to the P15V mosfet Drain at P-Board, the 2.38V on P15V rail is the gate voltage leaking into the circuit, so with that it can bypass SOUND_SOS, plugging the ribbon from D20 to SC leads the SC to consume some power from the P15V rail, dropping it to 1V, so SOUND_SOS activates.