50PK750 keeps blowing resistor!! HELP

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  • football0062
    Senior Member
    • Dec 2011
    • 98
    #1

    50PK750 keeps blowing resistor!! HELP

    Have a LG model 50PK750. has the EAY60968801 power supply with the 2 resistors in the top right.

    The problem is it keeps blowing either of the power resistors(22Ohm 5W) after shutting it down and turning back on.

    Ive replaced it with a used power supply which did the same thing
    Ive rebuilt the power supply and replaced the current control IC and Diode
    Ive replaced the Y sustain board and upper and lower buffer boards.

    attached pictures of the power supply. in red is the power resistors that keep blowing. in blue is the current control IC and diode i replaced.

    once it blows the resistor it turns on for a quick second and clicks back off.
    Attached Files
    Last edited by football0062; 02-11-2015, 09:31 PM.
    Tags: None
    • tom66
      EVs Rule
      • Apr 2011
      • 32560
      • UK
      #2
      Re: 50PK750 keeps blowing resistor!! HELP

      Are you using "pulse rated" resistors? They are used to discharge Vs/Va on power off so have to withstand a large current pulse.
      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.

        Comment

        • football0062
          Senior Member
          • Dec 2011
          • 98
          #3
          Re: 50PK750 keeps blowing resistor!! HELP

          i wish i had the datasheet for it but im using these 5WJ22.
          Attached Files

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK
              #4
              Re: 50PK750 keeps blowing resistor!! HELP

              You might have to source some alternatives. They are probably generic 22 ohm resistors. Peak power dissipation will be 1,910W (205V Vsus assumed), so general purpose ones will just fuse open.
              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.

                Comment

                • football0062
                  Senior Member
                  • Dec 2011
                  • 98
                  #5
                  Re: 50PK750 keeps blowing resistor!! HELP

                  what would you recommend?

                    Comment

                    • football0062
                      Senior Member
                      • Dec 2011
                      • 98
                      #6
                      Re: 50PK750 keeps blowing resistor!! HELP

                      and yes vs is right at 205V so ur correct on the power dissipation

                        Comment

                        • football0062
                          Senior Member
                          • Dec 2011
                          • 98
                          #7
                          Re: 50PK750 keeps blowing resistor!! HELP

                          what do you think about this one?
                          Attached Files

                            Comment

                            • tom66
                              EVs Rule
                              • Apr 2011
                              • 32560
                              • UK
                              #8
                              Re: 50PK750 keeps blowing resistor!! HELP

                              Can you get the AC03,AC04,AC05,AC07 or AC10 series? (Other ones will be no good.) Charts on page 5 show max peak power is too low for AC01. Try and get as high as possible (AC10 is highest)
                              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.

                                Comment

                                • football0062
                                  Senior Member
                                  • Dec 2011
                                  • 98
                                  #9
                                  Re: 50PK750 keeps blowing resistor!! HELP

                                  i ordered the AC10 its a 7W 22ohm from digikey. i fly out to see family for a week tomorrow so part should be here when i return and i will post my findings. thank you

                                    Comment

                                    • football0062
                                      Senior Member
                                      • Dec 2011
                                      • 98
                                      #10
                                      Re: 50PK750 keeps blowing resistor!! HELP

                                      so far so good, keeping fingers crossed

                                        Comment

                                        • budm
                                          Badcaps Legend
                                          • Feb 2010
                                          • 40746
                                          • USA
                                          #11
                                          Re: 50PK750 keeps blowing resistor!! HELP

                                          Do you have the diagram of the board, the resistors look to be connected in series (one for discharging through the MOSFET, and one of for supplying the VS) at the junction is connected to the Cathode of a diode, and the other end is connected to the Drain pin for discharging?
                                          Last edited by budm; 02-25-2015, 10:49 AM.
                                          Never stop learning
                                          Basic LCD TV and Monitor troubleshooting guides.
                                          http://www.badcaps.net/forum/showthr...956#post305956

                                          Voltage Regulator (LDO) testing:
                                          http://www.badcaps.net/forum/showthr...999#post300999

                                          Inverter testing using old CFL:
                                          http://www.badcaps.net/forum/showthr...er+testing+cfl

                                          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                          http://s807.photobucket.com/user/budm/library/

                                          TV Factory reset codes listing:
                                          http://www.badcaps.net/forum/showthread.php?t=24809

                                            Comment

                                            • tom66
                                              EVs Rule
                                              • Apr 2011
                                              • 32560
                                              • UK
                                              #12
                                              Re: 50PK750 keeps blowing resistor!! HELP

                                              I don't have a diagram myself but the way it usually works is Vs connects to FET drain through 22 ohm resistor, and Va connects to same FET through another resistor. The transistor is turned on by the control IC on power fail to discharge Vs/Va.
                                              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.

                                                Comment

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