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Vizio s3851w-d4 power supply schematics

Discussion in 'Datasheets, Manuals and Component Identification' started by vizioUsr, Jan 23, 2018.

  1. ryanbahr


    Jul 21, 2018
    Greetings everyone,

    Replacing the small capacitor on my power supply board (different sound bar (S4251w-B4), same power supply board) fixed everything. It was the only capacitor to have any type of bulge, and it was a very minor bulge at that.

    I'm not sure why the 5V was wired to the standby. May be a revision, or a standby by-pass. Looks like it was done post assembly though, or possibly a failure of the mask to prevent the solder from flowing.
  2. yudhidel


    Aug 3, 2018
    Hi All,

    I have a very similar issue on the exact same model. I have repeated the following behaviors multiple times, when the main board is not connected to the switching board-
    1. Originally, 5v is on, but no STBY and no 24v.
    2. If I connect STBY to 5v, 24v is turned on.

    Noticing this, I added a switch between STBY and 5v, and connected the main logic board. However, with the main connected, I see the power LED flash and read the voltage for a moment I plug in the power, and it immediately starts dropping. After this, even if I disconnect the main and try measuring the output at switch board by itself, I don't get any readings! I discovered that if I discharge the capacitors C1 and C3, I can replicate the #1 and #2 above.

    It appears certainly some component in the switch board is faulty, however not sure what to check for there. Please suggest.
    Last edited: Aug 3, 2018
  3. nhc14


    May 16, 2019
    I have a VIZIO SB3851-C0 soundbar that recently stopped working (it no longer turns on). I see this is a trend. There is no C21 capacitor marked on the board however I am sure it is probably one of the same capacitors it has just been labeled differently on my model. Does anyone have any advice on any alternative solutions if swapping out the caps doesn't work?
    dkinsel2 and eguy1010 like this.
  4. mmmike


    Jun 13, 2019
    Thanks for the info everyone.

    I was able to revive my Vizio SB4251 in 20 minutes after getting a capacitor and soldering kit on amazon

    There's nothing like fixing something to make you feel great and save a ton of $$$.

    Just like most, I just had to replace C21 and I was back in business. Note, it didn't even look bad (no bulging).
  5. dkinsel2


    Jun 24, 2019
    On what board did you find the C21 capacitor? I have a different soundbar but it’s still vizio. People have had a common capacitor with all soundbars and it seems that mine is different when it comes to the PSU board and logic board.
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