Vizio SV421XVT Standby On but no power on (don't hear "click")

[rocketeerbkw]

My TV died the other night. The vizio text on the front illuminates orange when I plug the TV in but pressing the power button (on the remote and tv) does not turn the TV on. I don't hear the "click" which I assume is a relay.

I'm doing the DC-DC Converter troubleshooting from the service manual:

J1-10 05.14v
J1-11 05.14v
J1-12 05.14v
J1-02 12.00v (power switch on and off)
J1-03 12.00v (power switch on and off)
J1-04 -04.10 mv (power switch on and off)

Not sure if I stop here because J1-04 didn't measure correctly? If I don't stop, I'm unsure how to measure U1 (seen in IMG_0119.JPG lower left quadrant).

Thanks very much!

[rocketeerbkw]

Re: Vizio SV421XVT Standby On but no power on (don't hear "click")

Here's the rest of the measurements from the service manual

U1
49530W
936104
pin 5 5.06v
pin 6 5.06v
pin 7 5.06v
pin 8 5.06v

U2
L213
G9117
pin 1 2.038v
pin 2 3.285v
pin 3 5.09v

U3
L313
G1084
pin 1 2.057v
pin 2 3.307v
pin 3 5.06v

U5
L313
G1084
pin 1 2.05v
pin 2 3.3v
pin 3 5.06v

U9
L313
G1084
pin 1 0.553v
pin 2 1.799v
pin 3 3.299v

U7
L213
G9117
pin 1 2.044v
pin 2 3.293v
pin 3 5.06v

U4
L213
G9117
pin 1 0.3mv
pin 2 1.251v
pin 3 3.308v

U6
L213
G9117
pin 1 6.83v
pin 2 8.08v
pin 3 11.95v

U10
L361
05627 OR G5627
pin 7 1.103v

[robbiec16]

Re: Vizio SV421XVT Standby On but no power on (don't hear "click")

The very bottom left cap in pic 2 looks like its bulging,may just be on my screen though.

[rocketeerbkw]

Re: Vizio SV421XVT Standby On but no power on (don't hear "click")

Just a bad angle. I can't find any evidence of bulging/leaking on the sides/top/bottom for any of the caps on the power board or main board.

[tom66]

Re: Vizio SV421XVT Standby On but no power on (don't hear "click")

All regulators appear good but where are the rest of the readings for U10?

[rocketeerbkw]

Re: Vizio SV421XVT Standby On but no power on (don't hear "click")

U10
L361
05627 OR G5627
pin 1 5.06v
pin 2 0.796v
pin 3 0v
pin 4 0.795v
pin 5 4.93v
pin 6 0v
pin 7 1.095v
pin 8 5.08v

Thx again!

[rocketeerbkw]

Re: Vizio SV421XVT Standby On but no power on (don't hear "click")

For anyone else with the same problem.

I measured PS_ON at 1.12v and INV_ON/OFF at 0v. Since the power board was outputting all the correct voltages, I guessed the mainboard was broken.

I replaced the mainboard and my TV works again. PS_ON now reads 2.89v and INV_ON/OFF 3.32v.

[budm]

Re: Vizio SV421XVT Standby On but no power on (don't hear "click")

Thanks for the repair feedback, you did the right thing by checking the PS_ON line and the INV_ON/OFF LINE to see what condition they are and pointed the problem to be the Main board.

[Korndog]

Re: Vizio SV421XVT Standby On but no power on (don't hear "click")

I have an almost identical problem with my SV421XVT except for the Vizio logo LED is constantly "white" rather than the standby "orange". No video/backlight and the remote/IR Sensor as well as the power button have no effect on power on/off, video, backlight or Vizio logo LED. Looked for bulging/leaking caps, blown fuses, hot ICs, burnt board, runs, resistors, etc.

Used the service manual troubleshooting matrices "Trouble of DC-DC Converter" & "Monitor Display Nothing"

Power supply/Inverter board: 0500-0412-0790
Main board: 3642-0722-0150 (5D)

DMM negative lead referenced to Power supply/Inverter J1-5,6,7 or 8 GND
J1-1 Standby is constantly 2.78VDC
J1-2 12VDC is constantly 11.98VDC
J1-3 12VDC is constantly 11.98VDC
J1-4 GND is 0.00VDC (listed as 12VDC in matrix)
J1-5 GND
J1-6 GND
J1-7 GND
J1-8 GND
J1-9 No contact pin present
J1-10 ST/+5V is 5.12VDC
J1-11 ST/+5V is 5.12VDC
J1-12 ST/+5V is 5.12VDC
J1-13 ST/+5V is 0.10VDC (not checked in matrix)
J1-14 DIM1 is 0.10VDC (listed in "Monitor Display Nothing" matrix for backlight)
J1-15 DIM2 is 0.10VDC (not checked in matrix)
J1-16 INV On/Off is constantly 2.70VDC (not checked in matrix)

J2-1 18V is constantly 18.20VDC
J2-2 18V is constantly 18.20VDC
J2-3 GND
J2-4 GND

U1-U7 & U9-U10 on the main board read nominal as per the matrix.

With main board connector removed J1-10,11,12 ST/+5V is 5.25VDC and I can toggle the 12V & 18V on/off with jumpers but still have no backlight.

Suspect the power supply board because the backlight does not work. I have one on order from eBay BUT the fact that the power button does not toggle the power supply 12V & 18V & Vizio logo LED gives me concerns about the main board as well.