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LG 47LD450 - Will work for a couple days, then dead set

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    #1

    LG 47LD450 - Will work for a couple days, then dead set

    Hey guys, This is a great community that has already helped me through some TV repairs. For that I thank you. Hopefully you can assist me with this one because I am very stumped and cant find any info on this issue.

    This TV will work perfect for a few days. Then you will go to power it up and there will be no power and no standby light. Measuring the standby pins at the power supply in this condition give a reading of 0V. Actually all pins going to the main board are 0V in this state.

    Unplugging the unit for a while will usually solve the issue for a few more days. This would point directly to capacitor issues would it not? I've checked most of the capacitors on the secondary side of the PS out of circuit and will continue checking them tonight.

    Am I on the right page here? I would like to repair this board on a component level as the Canadian Dollar exchange rate is horrendous at the moment and all boards i can find are priced in USD.

    I did post on the welcome page but it looks like I'm still blocked from posting attachments as indicated my the box in the bottom left.

    I have pictures I will post as soon as I see that I am able to
    Last edited by bmschiizz; 01-20-2016, 04:31 PM.
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    #2
    Re: LG 47LD450 - Will work for a couple days, then dead set

    small caps on the primary side or cracked soldering are main suspects.

    Comment

      #3
      Re: LG 47LD450 - Will work for a couple days, then dead set

      there is a issue with attaching pictures at the minute due to the server swop you can use imgur to upload the pictures for now.

      Comment

        #4
        Re: LG 47LD450 - Will work for a couple days, then dead set

        Check for burnt solder or dry joints within the power supply inductors.
        Did I leave the soldering iron on?

        Comment

          #5
          Re: LG 47LD450 - Will work for a couple days, then dead set

          By small caps do you mean the extremely small ones by the ICs?

          Would this close up be burnt joints? they are on 2 components labeled P605 to P608.

          I'm not sure what they are. they are the two black coin shaped components above the inductors
          Attached Files

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            #6
            Re: LG 47LD450 - Will work for a couple days, then dead set

            They look good. When you have no standby what are you measuring on the two main filter capacitors next to the two yellow transformers? You should have about 170 volts DC there. Be careful as this section is always hot
            Did I leave the soldering iron on?

            Comment

              #7
              Re: LG 47LD450 - Will work for a couple days, then dead set

              To my surprise when I reinstalled the board into the TV and plugged it in the TV went directly to the no standby light condition. This is the first time it has been dead after being unplugged for a while. And it had been a while as I removed and re-soldered a few caps for testing over the last few days.

              So the voltage across the main caps is 161V

              The voltages on the P201 connector to the main board are

              Power on 0V
              20V - 0V
              3.5V - 3.4V* thought I measured these as 0V before.
              12V - 0V
              error - 0V
              a.dim - 0V
              p.dim - 0V

              Its been plugged in at least half an hour with no heat coming from anywhere on the power supply board
              Attached Files

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