Question about Vizio P2 42 in. HD-Ready Plasma Television

5 Answers

Vizio P42HDTV Power on Diagnosis

I have a Vizio P42HDTV that won't turn on.  I believe the main and sub power boards are ok, as all the voltages check out.
How can I tell whether the turn on issue is from the power supply versus the main (DTV) board?
The unit's power light comes on when I plug it in, but pressing the power button does not cause the led to cycle to green, nor do the main power relays click.

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  • 2 more comments 
  • DrAnonymous Apr 07, 2008

    Hi Bill, thanks for the info.  I did some more diagnosing and came up with the following:


    - When first plugged in, the relays do click.


    - After I press the power button, no clicking.


    - There is a switch on the main power board, that is labeled Auto/Normal.  If I switch it to Auto, the relays click and I can see the screen illuminate.  Its still black, but you can tell it came on.  No menu or video signal displayed.


    - If its unplugged for awhile and I plug it in, I can sometimes press the power button and the screen will come on with regular video for about 30 seconds. It will then click back off and pressing the power button won't do anything else.


    I almost wonder if its thermally related.


    Here's a link to a photo I took. 


    http://www.forumsigs.com/img.cfm?img=387...



    I labeled the parts. Do you think this is the DTV board? I think the Y/Z sustain boards are ok, since the image looks fine when it does come on.

  • DrAnonymous Apr 11, 2008


    I can't find a cap that's bad, but using this manual -

    nationalservicealliance.com/visio/VIZIO-P42HDTV10A.pdf




    I discovered most of the input voltages to the voltage regulators are not correct.  The 7809 should have at least 10V on pin 1 to regulate down to 9V on pin3.  My input was 1.26V, way too low.


    Here are the readings for my board -


    J1 All 5V lines good
    J1 All 12V lines good


    U4 3.3V output good
    U5 1.8V output good


    U6 0V output and 1.26V input. This is the 7809.
    U7 0V output
    U13 0.31V
    U14 0.31V


    J2 5V on all lines
    J7 Should read 3V or higher on the buttons (Power, volume, etc)


    I noticed that when my TV turned on I had the correct voltages on the buttons.  When it wasn't working, the button voltages were under a volt.  I never could catch the voltage at one of the regulators at the same time the button voltages worked.


    Vancebaldwin sells the board for $145'ish including shipping.  They have a core charge of $60'ish.  Unless I can get ahold of a schematic, it may be easier to just buy another board.


    I'd be happy to swap info with someone directly or via phone if they'd like.

  • Anonymous Apr 13, 2008

    Please check the U29 8 pin little surface mount mosfet it has this
    letters
    > FDS4935
    >
    > In this part inputs 13.2 volts which is ok for the near 12 vdc but
    it
    > outputs 1.250 vdc i am 100% sure that this is all the problem
    >
    > check it out, and tell me if you´re agree with me
    >
    > On this output pin it feeds the audio Ic, the 7809 and the tuner side
    board
    > which needs de 12vdc too and its getting only the 5vdc part
    >
    > what do ya think??
    >
    > Richard

  • importc Feb 05, 2009

    where is that board with pin 8 u29

    wont turn on p42 vizio

×

5 Answers

Please check the U29 8 pin little surface mount mosfet it has this letters > FDS4935 > > In this part inputs 13.2 volts which is ok for the near 12 vdc but it > outputs 1.250 vdc i am 100% sure that this is all the problem > > check it out, and tell me if you´re agree with me > > On this output pin it feeds the audio Ic, the 7809 and the tuner side board > which needs de 12vdc too and its getting only the 5vdc part > > what do ya think?? > > Richard

Posted on Apr 13, 2008

Please check the U29 8 pin little surface mount mosfet it has this letters > FDS4935 > > In this part inputs 13.2 volts which is ok for the near 12 vdc but it > outputs 1.250 vdc i am 100% sure that this is all the problem > > check it out, and tell me if you´re agree with me > > On this output pin it feeds the audio Ic, the 7809 and the tuner side board > which needs de 12vdc too and its getting only the 5vdc part > > what do ya think?? > > Richard

Posted on Apr 13, 2008

Please check the U29 8 pin little surface mount mosfet it has this letters > FDS4935 > > In this part inputs 13.2 volts which is ok for the near 12 vdc but it > outputs 1.250 vdc i am 100% sure that this is all the problem > > check it out, and tell me if you´re agree with me > > On this output pin it feeds the audio Ic, the 7809 and the tuner side board > which needs de 12vdc too and its getting only the 5vdc part > > what do ya think?? > > Richard

Posted on Apr 13, 2008

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Hi same problem, but which component is the problem?? i cant buy a new dtv board ill try ti fix it, but which caps are the faultys?? pls help

Posted on Apr 11, 2008

  • ricardito Apr 13, 2008

    I think i got it!!!


    Please check the U29 8 pin little surface mount mosfet it has this
    letters
    > FDS4935
    >
    > In this part inputs 13.2 volts which is ok for the near 12 vdc but
    it
    > outputs 1.250 vdc i am 100% sure that this is all the problem
    >
    > check it out, and tell me if you´re agree with me
    >
    > On this output pin it feeds the audio Ic, the 7809 and the tuner side
    board
    > which needs de 12vdc too and its getting only the 5vdc part
    >
    > what do ya think??
    >
    > Richard

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  • 934 Answers

Relays are the first big clue, triggered by the 5 & 12v supply you should be able to trace back using a dmm and see if you have both of those voltages present... The lead coming from the smps to the y-sus board is a good start. On a Vizio I believe the voltages are listed per pin right on the board...
If you had any kind of relay sound then you could suspect the y-sustain or z-sustain board or something else. With the relays being silent I'd strongly suspect the power supply.
Bill

Posted on Apr 06, 2008

  • William Rayburn
    William Rayburn Apr 07, 2008

    Could very well be thermal affected - and somewhere in the cause and symptom it's likely to include being some caps will need to be replaced. Don't rule out the sustain boards - they could very well be loading down the supply and cause these very symptoms. You might try unplugging first the x-sus from the supply and try to power the unit. If it comes up normally (picture messed up of course) powers okay has audio then try testing the components on the x-sus. Then try the same thing with the y-sus. At this point you'll need to take out the schematics and mesaure some test points to isolate the problem. While you're at it, might as well get out the esr meter and some mist and check on a few caps - might help narrow down the area too..

    Good Luck!

    Bill

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