LG 50pv400 Plasma Display issue

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  • smuddge
    Senior Member
    • Feb 2012
    • 96
    • Canada

    #1

    LG 50pv400 Plasma Display issue

    Not sure what happened with this tv.
    Was working fine then yesterday when i turned it on I was greeted with a washed out display that is essentially black and white.
    All settings and images display but there is no colour in them.
    I spoke with a few people who said its the plasma panel that is bad and that the tv is garbage, however everyone of them said they wanted the tv which confused me.

    I have posted on this website before and got awesome results. (every tv I have ever posted about I was given the exact problem and each time it has fixed the tv)

    I have a great deal of respect for the members here so I thought I would see what the real deal is on this.

    If it is infact bad I will part it out

    here is a picture of the display if it helps out.

    Thanks in advance for any replies.


  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: LG 50pv400 Plasma Display issue

    That doesn't look like a bad panel to me.
    Can you post a picture of the parts inside?
    Could be Vzbias or Vset_up fault, leaning towards Vset_up myself.
    (These are voltages which drive the plasma panel, they can go bad or missing...)
    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

    • smuddge
      Senior Member
      • Feb 2012
      • 96
      • Canada

      #3
      Re: LG 50pv400 Plasma Display issue

      camera is an iphone 4. not great quality but if you need something clearer i will try and get a close up of something if required.

      I am a novice with this stuff also just to let you know.
      I am good with a soldering iron but not much experience measuring voltage.
      I have had a bad experience when I was fixing a microwave and got a shock that I will not soon forget. LOL





      Comment

      • dabyd64
        Member
        • May 2013
        • 27
        • spain

        #4
        Re: LG 50pv400 Plasma Display issue

        Hope this helps: (450 is almost the same as the 400)

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK

          #5
          Re: LG 50pv400 Plasma Display issue

          On the back internal metal chassis there's a sticker marked LG Electronics PDP50K9 for example, what does yours say exactly?
          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

          • smuddge
            Senior Member
            • Feb 2012
            • 96
            • Canada

            #6
            Re: LG 50pv400 Plasma Display issue

            Originally posted by tom66
            On the back internal metal chassis there's a sticker marked LG Electronics PDP50K9 for example, what does yours say exactly?

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: LG 50pv400 Plasma Display issue

              This document, page 139 has PDP50R3:


              Of most interest are page 143 for -Vy and Vsc, and page 148 for Vzbias checks. Page 141 Vs and Va should also be checked.

              Can you check these voltages, comparing to the panel sticker:
              -Vy: -190V
              Vsc: 150V
              Vzbias: 130V
              Last edited by tom66; 02-27-2014, 09:14 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

              • smuddge
                Senior Member
                • Feb 2012
                • 96
                • Canada

                #8
                Re: LG 50pv400 Plasma Display issue

                sorry i took so long to get back to this thread. just had emergency Appendectomy.

                As I said before I have very little experience with measuring voltage etc.

                I am trying to measure the voltages of the VSC and -vy but I get nothing on the multimeter. just sitting at 1. i assume i have the multimeter set right. I have it on V- and at 200. is the tv supposed to be on or off. I am measuring it with it on and i get nothing with it off it has a voltage that drops slowly until it gets to 0.

                sorry for the newbie question but I am just learning this as I go.

                Comment

                • smuddge
                  Senior Member
                  • Feb 2012
                  • 96
                  • Canada

                  #9
                  Re: LG 50pv400 Plasma Display issue

                  think i am doing it right. i get vzb reading of 124v
                  va says 4.8v
                  vs i don't know how to check as I have no test points on the resistor.
                  i see it says use p811 pin 6 but i don't know what to put the other black tester to....

                  Comment

                  • tom66
                    EVs Rule
                    • Apr 2011
                    • 32560
                    • UK

                    #10
                    Re: LG 50pv400 Plasma Display issue

                    Black will go to the metal chassis. Va is really low, are you sure about that?
                    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

                    • smuddge
                      Senior Member
                      • Feb 2012
                      • 96
                      • Canada

                      #11
                      Re: LG 50pv400 Plasma Display issue

                      re-tested them all
                      -vy flashes various voltages and stops at 1
                      vsc flashes various voltages and stops at 1
                      vzbias 129.9v
                      vs shows 5.0v on the 200 setting of my multimeter and 5.04 on the 20 setting
                      va show 202v

                      Comment

                      • tom66
                        EVs Rule
                        • Apr 2011
                        • 32560
                        • UK

                        #12
                        Re: LG 50pv400 Plasma Display issue

                        Are you using DC range, or AC? Va should measure in the 50-to-60 volt range. 200V would kill the panel very quickly (smoke & bang.) Maybe you're mixing Va and Vs up, and Vs and 5V.

                        Please try the next highest range on your meter usually 500V,600V or 1000V for all voltages. Make sure it is DC (marked by line and dash symbol, not the ~ symbol.)
                        Last edited by tom66; 03-07-2014, 11:13 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

                        • smuddge
                          Senior Member
                          • Feb 2012
                          • 96
                          • Canada

                          #13
                          Re: LG 50pv400 Plasma Display issue

                          i am using DC when measuring.
                          i mixed up when posting

                          vs showing 202v
                          va shows 5.0v on the 200 setting of my multimeter and 5.04 on the 20 setting
                          va on 600 setting shows 0
                          Last edited by smuddge; 03-07-2014, 11:42 AM.

                          Comment

                          • tom66
                            EVs Rule
                            • Apr 2011
                            • 32560
                            • UK

                            #14
                            Re: LG 50pv400 Plasma Display issue

                            Please show me the location you are using to check Va with a picture.
                            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

                            • Alastair E
                              Chief Womble
                              • Mar 2013
                              • 1963
                              • U.K.

                              #15
                              Re: LG 50pv400 Plasma Display issue

                              Hmm....

                              IF Va was only 5v there wouldnt be Anything on the screen.
                              --This is the 'Address' voltage thats used to prime-up the pixels before they are discharged to make light, using the Vs supply-- Normally this Va voltage is between 50 and 70v depending on make/model etc....

                              The V-Zbias and -Vy missing could give symptoms like you have, as well as other issues on the Z-SUS board....
                              TELEFIX

                              How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
                              http://www.irf.com/technical-info/appnotes/an-1088.pdf
                              PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

                              Comment

                              • smuddge
                                Senior Member
                                • Feb 2012
                                • 96
                                • Canada

                                #16
                                Re: LG 50pv400 Plasma Display issue

                                here are the 2 places i measured VA


                                Comment

                                • tom66
                                  EVs Rule
                                  • Apr 2011
                                  • 32560
                                  • UK

                                  #17
                                  Re: LG 50pv400 Plasma Display issue

                                  The first one is not a test point unfortunately, the second one looks like M5V? which would explain the 5V reading. Can you lift the blue disc capacitor and see if there is a pin marked 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

                                  • Alastair E
                                    Chief Womble
                                    • Mar 2013
                                    • 1963
                                    • U.K.

                                    #18
                                    Re: LG 50pv400 Plasma Display issue

                                    Ah--There you go, wrong place to measure it!

                                    Looking at that PSU board, there'll be a plug with thick leads going to the boards to left and right of it.

                                    These thick leads at the plug on the PSU will be marked, Vs and Va and maybe other voltages too.

                                    Its at these leads in the plug is where to measure the voltage, you can stick the meter-probe down the side where the lead attaches the metal part of the plug, the other meter lead to the metal frame of the set.....
                                    TELEFIX

                                    How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
                                    http://www.irf.com/technical-info/appnotes/an-1088.pdf
                                    PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

                                    Comment

                                    • smuddge
                                      Senior Member
                                      • Feb 2012
                                      • 96
                                      • Canada

                                      #19
                                      Re: LG 50pv400 Plasma Display issue

                                      sorry looking at the pdf it said
                                      VA ADJUST: Connect DVM to VA Test Point or pins 6 of P811

                                      however when i moved the blue cap out of the way it shows va as the pin 5.

                                      anyways va is 54.4v

                                      sorry again i am new to this but learning quick. LOL

                                      Comment

                                      • tom66
                                        EVs Rule
                                        • Apr 2011
                                        • 32560
                                        • UK

                                        #20
                                        Re: LG 50pv400 Plasma Display issue

                                        So Vs and Va match panel sticker? Now please check -Vy, Vsc and Vzbias voltages in the same manner.
                                        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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