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LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

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    #21
    Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

    Good fix, thanks for the update.
    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

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      #22
      Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

      I'm chasing somewhat of the same issue. Started with a shorted cap at c204 between Vcc and gnd of Ic201 (200d6). replaced with a 50uf (original was 100) to check and everything worked for about 10min.
      replaced Ic201 based on OP's xperiences as everything else seemed to test fine, as well as replacing C204 with the proper value.
      Blew out the 2.0 ohm resistor and the driver FET Q202.
      replaced those and IC201 again(as a precaution), and got fluctuating voltages on the high voltage pin of IC201 .
      IC201 was showing high frequency bursts on the gate of the FET, and as I was continuing to probe it blew out the 2.0 ohm resistor and the FET again.
      I've checked all around that area and components seem fine.
      Any advice?

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        #23
        Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

        If i remember correctly I blew the same FET and resister once because I had the ic-201 removed from the circuit when I powered up the board. IF I remember correctly there is a small transformer located next to the IC-201, FET and resistor. Make sure incoming/outgoing voltage is good on that. make sure all connections and solder joints are good in the area also. A cold solder joint will cause some weird symptoms and have you chasing ghost.

        Also remember there is a floating ground and a chassis ground on that board.

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          #24
          Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

          Thanks, I've given the board a good look over, but I'm sure my tired old eyes may have missed something.
          I'll report back when I've had another go at it.

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            #25
            Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

            Just gave up and bought a used y-sus for $45. back up and running!

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              #26
              Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

              Hey as long as it is working.

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                #27
                Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

                I am looking for C417 and C418 value. Does the rated value is 500v ?
                Thank you.

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                  #28
                  Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

                  Originally posted by alain28 View Post
                  I am looking for C417 and C418 value. Does the rated value is 500v ?
                  Thank you.

                  I no longer have this tv, but ill look around in my notes and pictures and see what i can find for you.

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                    #29
                    Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

                    I believe they are 0.022uF

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                      #30
                      Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

                      Thank you very much for the answers of Beau28713 & R_J
                      You can see a picture of these caps here:
                      http://www.coppelltvrepair.com/p/154...-image-problem

                      On the left and right they are C416/415 & C401/402 that seems similar to the couple C417/418.
                      The dielectric is light grey then the value could be low but also different because the height is not the same.


                      It is not for me but a colleague so I Don't have the board.

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                        #31
                        Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault

                        I do believe R_J is correct in saying they are .022uF and around 500v. The safest way to proceed would to just buy the repair kit. That way you will have the correct caps and plus you will have some spare parts in case you need them.

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