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Vizio VX32L no 12v

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    #21
    Re: Vizio VX32L no 12v

    Originally posted by Mr Bill View Post
    If i measure pin 1 (Mosfet source/overcurrent protection) to ground i get 0.006 ohm.
    One page 9 of the datasheet, there is a typical applicaton circuit. There is a resistor connected to pin 1. If it is a low ohm resistor, it could explain the low reading.

    In addition, in circuit measurements are not always 100% reliable due to other components in parallel.

    If the IC is shorted, I normally measure the resistance between VCC and GND. That is, pin 5 and pin 3 for your IC.

    If it is not shorted, then I measure the DC voltage on VCC wrt to IC GND. According to the datasheet (page 5), it should be 14.3V for the IC to start properly.

    I also measure the DC voltage across the cap that is tied to VCC to make sure it is around 14.3V.

    So try all the above first.
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      #22
      Re: Vizio VX32L no 12v

      From vcc to ground it's not shorted. I plugged the power supply in and i'm getting 15.45v on the vcc pin. I'm getting the same reading on the cap that is on the same circuit as pin 5 (vcc).

      Comment

        #23
        Re: Vizio VX32L no 12v

        Originally posted by Mr Bill View Post
        Here is a picture of the bottom of the power supply.
        What is the part number of these two ICs?
        Attached Files
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          #24
          Re: Vizio VX32L no 12v

          Originally posted by retiredcaps View Post
          What is the part number of these two ICs?
          The little ic is:

          4863-2
          Power Factor Controller IC

          The big one is:

          L6598
          HIGH VOLTAGE RESONANT CONTROLLER

          Neither are shorted from vcc to ground.
          Attached Files

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            #25
            Re: Vizio VX32L no 12v

            Originally posted by Mr Bill View Post
            I removed D7, D8, & D9 and they are good.
            Okay, here is what I'm trying to find out by using some divide and conquer.

            We know at the connector we are missing 12V. That is what I call the "end point". The "start point" is the SMPS IC. If the voltage going to VCC pin matches the datasheet, then let's assume the SMPS IC is working.

            The D7, D8, and D9 diodes are what I call the "mid point". One of these dual diodes (I'm assuming they are 3 pin and look like -><-) is responsible for outputting 12V DC (all 3 sit on the secondary side of the board).

            So at the "mid point", let's measure the DC voltage of each the middle pin diode wrt to ground. If we get 12V DC on one of them, then the missing 12V problem lies between the diode and the connector. If we don't get 12V DC, then the problem lies between the SMPS IC and the diode.
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