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LG 42LE5900 PSU issue

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    #1

    LG 42LE5900 PSU issue

    I've recently inherited an LG 42LE5900 via a friend; who got it off a colleague who upgraded to something better.

    Unfortunately, having powered it up there is a loud buzzing noise from the power supply – increasing when there is a increase in the load on the PSU.
    I've cracked it open, the caps on the front side all look fine, the output voltages are okay etc; but that's as far as I can get with the LG service manual - which doesn't cover the power board…

    Looking at the back of the board, it looks like one of the surface mount diodes may have overheated.

    The diode is D204, its located near the mechanical relay so may well be a flyback diode; one end terminates on the ground plane. I'm slightly limited in the diagnostic equipment I have available but it is reading 31 ohms in both directions which might suggest a short.

    Is anyone in possession of any schematics for the EAY60803201 or had a similar experience with one of these TVs?
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    #2
    Re: LG 42LE5900 PSU issue

    Take that diode out and measure it out of circuit.

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      #3
      Re: LG 42LE5900 PSU issue

      That diode is across the relay coil, it is not your problem.
      Originally posted by dave2020 View Post
      I’ve recently inherited an LG 42LE5900 via a friend; who got it off a colleague who upgraded to something better.

      Unfortunately, having powered it up there is a loud buzzing noise from the power supply – increasing when there is a increase in the load on the PSU.
      I’ve cracked it open, the caps on the front side all look fine, the output voltages are okay etc; but that’s as far as I can get with the LG service manual - which doesn’t cover the power board…
      So the tv IS working? If not what are you doing to increase the load on the power supply?
      Last edited by R_J; 03-01-2020, 11:21 AM.

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        #4
        Re: LG 42LE5900 PSU issue

        The TV works, the loud buzzing is a bit concerning though..

        Using the menu system or displaying anything white increases the load enough to make the buzzing really quite loud.

        If you power it up with the back off, the noise does seem to be located around the pair of (what I assume are) inductor coils- labelled 10S-LP01 B. Though it could equally be from the large voltage regulator under the adjacent heatsink..

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          #5
          Re: LG 42LE5900 PSU issue

          Those coils are in the PFC circut, they could make a squealing noise if the coils are a bit loose. I would not be too concerned.

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