Vizio P50HDTV20A power supply - Vs problem

[DakotaKid]

I have a Vizio P50HDTV20A 50" plasma with a power supply, mainboard, connector board problem. I get no picture, not sure about sound because I haven't hooked source to it yet. No visible problems with caps although they appear to be originals from 2007 when TV was made. I cannot find the manual for this specific model, it is different than the HDTV10A and the HDPM that some have listed for this TV isn't the right power supply. Panel is Samsung S50HW-YD02. Panel voltages on label are Va=63, Vsc=-195, Vs=207, Ve=94.

With power on and X and Y boards disconnected from power, D5V and D3V3 values are about as expected at 5.03V and 3.4V. Test points on the PS board show: A12V=11.94V, V24amp = 23.3V, Vt=31.7V, Vg=14.6V, Vs=1.59, Va=61.1V, 5Vsb=4.99. Fuse F110 and F251 test as good and show 326V when the TV is powered on. The fault LED1 is not lit or flashing.

The symptom is that Vs is 1.59V instead of 200+. Without SM I don't know the origin of this voltage and whether a signal from another board is keeping it from coming on.

I will retake the pictures when I can. Power Supply is Samsung model PSPF561A01A rev DR3 0.8 Date 071020

Any suggestions to track down Vs problem? Is there a way to force this PS on if there is a signal from another board missing?

[tom66]

Re: Vizio P50HDTV20A power supply - Vs problem

Vs could be low due to shorted sustain board.

[DakotaKid]

Re: Vizio P50HDTV20A power supply - Vs problem

Vs could be low due to shorted sustain board.

The voltage readings were all taken with the X and Y plugs all disconnected. Vs is low with no load at all.

[DakotaKid]

Re: Vizio P50HDTV20A power supply - Vs problem

Ok, I pulled this TV back out of my queue and pulled the power supply to put it on the bench so I can hopefully repair it. I need a little help as I want to force the power supply on. A couple of questions first. I have a power pigtail from a different TV with a plug that matches this board connector with the blue and brown wire 120V inputs. Does polarity matter on whether the brown or blue is the hot or neutral leg of the incoming AC? This one is opposite of what the Vizio has and I can easily switch them around if necessary.

Since it is the Vs portion I am concerned with do I need to energize the PS_on and the Vs_on both with 5v? I have attached pictures of the connectors on the PS and the Vs section of the board top and bottom. There doesn't seem to be any damage on the bottom of the board and no obvious bad components on the top side e.g. no bulging or leaking caps, no scorching, no blown fuses.

Power supply is Samsung LJ44-00132B model PSPF561A01A Rev DR3 0.8 with Vamp = 24VDC.

I am looking for what might be causing the low voltage on Vs. Maybe what Tom66 was saying is that Vs_on or PS_on where not going high because of a fault elsewhere. What should I do to check that?

Thanks in advance.
DK