LG 42PC5D Plasma no pic but sound

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  • maddog310
    Senior Member
    • Apr 2010
    • 51
    • Canada

    #1

    LG 42PC5D Plasma no pic but sound

    Hi, have another one here to attempt to fix.
    Did the light bulb trick, no light with boards connected or disconnected.
    Three green leds on control board lit, i believe there are four, and one on main board.
    Two 450v 270uf Nichicon caps look slightly bulged.

    Took some voltage readings at the connectors. VS :190v, VA :60v on the sticker.

    P11 to xmain

    VS : 189.8v
    VS : 189.8v
    NC :
    GND :
    GND :
    VA : 59.3v
    GND :
    5V :4.98v

    P12 to y board

    VS : 189.8v
    VS : 189.8v
    NC :
    GND :
    GND :
    GND :
    VA : 59.3v
    GND :
    5V : 4.99v

    P3 to main board

    3.4v : 3.421v
    3.4v : 3.421v
    GND :
    GND :
    6v : 6v
    6v : 6v
    GND :
    GND :
    12V : 12.09v
    12v : 12.09v
    GND :
    GND :

    P2 to main board

    19v : 19.05v
    19v : 19.05v
    GND :
    GND :
    6v : 6v
    GND :
    3.4V : 3.422V
    GND :
    12v : 12.09v
    GND :

    P1 to main board

    AC DET : 4.85v
    RL ON : 5.06v
    STB5V : 5.07v
    GND :
    VS ON : 5.03v
    5V DET : 4.47V
    M5V ON : 5.06v
    STB5V : 5.06v
    GND :
    NC :
    6V : 6v
    GND :
    3.4V ON : 5.06V

    P103 y main connector

    +5V : 4.98v
    GND :
    +VA : 59.2v
    GND :
    GND :
    GND :
    NC :
    +VS : 189.6v
    +VS : 189.6v

    P1 x main connector

    +VS : 189.7v
    +VS : 189.7v
    NC :
    GND :
    GND :
    VA : 59.2v
    GND :
    +5V : 4.95v

    Anyone have any thoughts on these figures, pics to follow.
    I have read it could possibly be a ipm on y board!

    Any help is appreciated.
  • maddog310
    Senior Member
    • Apr 2010
    • 51
    • Canada

    #2
    Re: LG 42PC5D Plasma no pic but sound

    Here are a few pics.
    Attached Files

    Comment

    • tom66
      EVs Rule
      • Apr 2011
      • 32560
      • UK

      #3
      Re: LG 42PC5D Plasma no pic but sound

      On the top left of the Y-sus you have a bank of five red capacitors:
      https://www.badcaps.net/forum/attach...5&d=1365742983

      Check the voltage across any of these (they are in parallel.) What do you measure?
      Last edited by tom66; 04-12-2013, 03:31 AM.
      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

      • maddog310
        Senior Member
        • Apr 2010
        • 51
        • Canada

        #4
        Re: LG 42PC5D Plasma no pic but sound

        Tom66, it seems to fluctuate between 98.5v and 95.5v approximately.

        Comment

        • maddog310
          Senior Member
          • Apr 2010
          • 51
          • Canada

          #5
          Re: LG 42PC5D Plasma no pic but sound

          So i took the Y and Z boards out and checked the IPM's, they appear to be bad by the values i measured.

          Tested in diode mode.

          Ysus
          Forward
          Test 1: GND + SUS OUT - = .345v
          2: SUS OUT + VS - = .341v

          Diode value over 0.4v = OK

          Reverse
          Test 1: GND - SUS OUT + = OL
          2: SUS OUT - VS + = OL

          Diode value is infinity = OK

          Zsus
          Forward
          Test 1: GND + SUS OUT - = .346v
          2: SUS OUT + VS - = .347v

          Diode value over 0.4v = OK

          Reverse
          Test 1: GND - SUS OUT + = OL
          2: SUS OUT - VS + = OL

          Diode value is infinity = OK

          Here are the pages i found for testing.
          Attached Files

          Comment

          • maddog310
            Senior Member
            • Apr 2010
            • 51
            • Canada

            #6
            Re: LG 42PC5D Plasma no pic but sound

            On the control board there are four Temp Diodes, D1, D2, D3, and D4.
            Three of them are lit and D1 is not.
            Does any one know if this is connected with these IPM's?

            Comment

            • maddog310
              Senior Member
              • Apr 2010
              • 51
              • Canada

              #7
              Re: LG 42PC5D Plasma no pic but sound

              Pic of diodes on control board are on page 57 of this manual.
              Would have uploaded only that page but wasn't able to.
              Attached Files

              Comment

              • tom66
                EVs Rule
                • Apr 2011
                • 32560
                • UK

                #8
                Re: LG 42PC5D Plasma no pic but sound

                The LEDs are good. All lit is bad. Otherwise is OK.

                I have had bad IPM which tested good on meter (diode test) but was dead anyway. Sometimes it would make a ticking/clicking sound.

                You need to compare the voltage on the Y-sus caps to the same on the Z-sus' five red caps.
                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

                • maddog310
                  Senior Member
                  • Apr 2010
                  • 51
                  • Canada

                  #9
                  Re: LG 42PC5D Plasma no pic but sound

                  Ysus caps read 96.1v and Xsus is 87.2v, both fluctuate a little, five red caps.

                  If i were to change the ipm's, what should i be checking before installing them, so they don't get fried!
                  Where could i get these, part # AEF31675201(A), 0651SANY(P).

                  Comment

                  • hienton2
                    Senior Member
                    • Sep 2009
                    • 183

                    #10
                    Re: LG 42PC5D Plasma no pic but sound

                    Maddog310.

                    My plasma problem is very much same as yours.
                    https://www.badcaps.net/forum/showthread.php?t=27960

                    Do you feel any warm on the ipm z sus and y sus.
                    Mine z sus ipm is very cold when tv running. Y sus is warm.

                    Comment

                    • maddog310
                      Senior Member
                      • Apr 2010
                      • 51
                      • Canada

                      #11
                      Re: LG 42PC5D Plasma no pic but sound

                      Hey hienton2, as i recall both were warm, check out these two treads.

                      https://www.badcaps.net/forum/showthread.php?t=14214

                      https://www.badcaps.net/forum/showthread.php?t=8920

                      Possibly it's blown also!

                      Comment

                      • tom66
                        EVs Rule
                        • Apr 2011
                        • 32560
                        • UK

                        #12
                        Re: LG 42PC5D Plasma no pic but sound

                        The bad ones on mine were warm too, I recall.
                        Which one is fluctuating? Are both fluctuating?
                        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

                        • maddog310
                          Senior Member
                          • Apr 2010
                          • 51
                          • Canada

                          #13
                          Re: LG 42PC5D Plasma no pic but sound

                          Originally posted by maddog310
                          Ysus caps read 96.1v and Xsus is 87.2v, both fluctuate a little, five red caps.

                          If i were to change the ipm's, what should i be checking before installing them, so they don't get fried!
                          Where could i get these, part # AEF31675201(A), 0651SANY(P).
                          I believe these voltages are good from what i have read, any where from 60v to 120v is good!

                          I think i have bad components on ysus, diodes and mosfets around the 15v section.

                          Details to follow.

                          Comment

                          • tom66
                            EVs Rule
                            • Apr 2011
                            • 32560
                            • UK

                            #14
                            Re: LG 42PC5D Plasma no pic but sound

                            Which voltage on the ERC caps was fluctuating?

                            60V to 120V is a general rule, if you have a good meter, measure the output on DC VRMS of the sustain board and across the caps, it should be nearly the same (+/-5%); that is the best test.
                            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

                            • maddog310
                              Senior Member
                              • Apr 2010
                              • 51
                              • Canada

                              #15
                              Re: LG 42PC5D Plasma no pic but sound

                              Originally posted by tom66
                              Which voltage on the ERC caps was fluctuating?

                              60V to 120V is a general rule, if you have a good meter, measure the output on DC VRMS of the sustain board and across the caps, it should be nearly the same (+/-5%); that is the best test.
                              Both voltages at the five red caps fluctuate.
                              Ysus caps read 96.1v and Xsus is 87.2v, both fluctuate a little, five red caps. Copied from previous post.

                              I checked diodes at D202, D203, D204, D205 plus others on ysus.
                              I get in diode mode.

                              D202 forward .434v reverse .790v
                              D203 forward .433v reverse .841v
                              D204 forward .446v reverse OL
                              D205 forward .443v reverse OL

                              So it looks like the first two are bad! Checked others on the board and they test like the last two.

                              Also checked Q1 and Q2 mosfets.

                              Q1 D to S 160.8 kohms
                              Q2 D to S OL

                              Looks like Q1 is bad! That heat sink was very hot also.

                              Is there anything else i should be checking? resistors?

                              The bad diode has F46J on it, I can't seem to find a replacement.
                              Pics of ysus.
                              Attached Files

                              Comment

                              • maddog310
                                Senior Member
                                • Apr 2010
                                • 51
                                • Canada

                                #16
                                Re: LG 42PC5D Plasma no pic but sound

                                Any thoughts on what I've posted!

                                Comment

                                • tom66
                                  EVs Rule
                                  • Apr 2011
                                  • 32560
                                  • UK

                                  #17
                                  Re: LG 42PC5D Plasma no pic but sound

                                  Q1 G-S and G-D too.
                                  D's need to be verified out of circuit as they may be OK.
                                  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

                                  • maddog310
                                    Senior Member
                                    • Apr 2010
                                    • 51
                                    • Canada

                                    #18
                                    Re: LG 42PC5D Plasma no pic but sound

                                    Q1
                                    D to S 160.8 kohms
                                    G to S 5.2 kohms
                                    G to D 235 kohms

                                    Q2
                                    D to S OL
                                    G to S 37.66 kohms
                                    G to D 7.44 Mohms
                                    Last edited by maddog310; 04-17-2013, 02:47 PM.

                                    Comment

                                    • tom66
                                      EVs Rule
                                      • Apr 2011
                                      • 32560
                                      • UK

                                      #19
                                      Re: LG 42PC5D Plasma no pic but sound

                                      The G-S is very suspicious, so you will need to remove it (or disconnect two leads) and re-test the resistance.
                                      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

                                      • maddog310
                                        Senior Member
                                        • Apr 2010
                                        • 51
                                        • Canada

                                        #20
                                        Re: LG 42PC5D Plasma no pic but sound

                                        Ok, will do..... Q1.

                                        What do you think of the values of these diodes also.
                                        I checked diodes at D202, D203, D204, D205 plus others on ysus.
                                        I get in diode mode.

                                        D202 forward .434v reverse .790v
                                        D203 forward .433v reverse .841v
                                        D204 forward .446v reverse OL
                                        D205 forward .443v reverse OL

                                        So it looks like the first two are bad! Checked others on the board and they test like the last two.

                                        Comment

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