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LG 60PZ750 running hot and maldischarged

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    LG 60PZ750 running hot and maldischarged

    Hi All, I have a 60PZ750 that I repaired the EBR73561701 Zsus board. Tv runs good for about 30 min to an hour then the picture looks maldischarged with red & green snow sparkles on lighter pictures, also I noticed the TV seems to run hotter that the usual plasma's. All my voltages seem good.

    VS 201.2
    VA 55.07
    5V 5.13
    VSC 150V
    VZB 105.5

    I have no history on this TV as I picked it up for cheap "not working". On the Szuz board I replaced the fuse, 6 FGPF4633 transistors and the 12 gate resistors. I have attached some pictures. Any help would be much appreciated. Tom if your out there I got myself a new digital scope
    Attached Files

    #2
    Re: LG 60PZ750 running hot and maldischarged

    There are SMD resistors and optocouplers who also can fail when IGBTs short,on solder side,check all optocouplers for low resistances between pins,and 10 or 100 OHMs resistors,ceramic capacitors.
    Last edited by Biruslapio; 03-23-2018, 03:22 PM.

    Comment


      #3
      Re: LG 60PZ750 running hot and maldischarged

      I'm not 100% certain but shouldn't Vzb when measured between the two points = -178V as shown on the white label.
      Willing to help but I'm no expert.

      Comment


        #4
        Re: LG 60PZ750 running hot and maldischarged

        Nice, show scope pics

        Vzb should be ~110V
        -Vy is -178V
        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


          #5
          Re: LG 60PZ750 running hot and maldischarged

          Are the SMD resistors the same as the gate resistors ? If so I did replace them if they are the two in parallel at the transistors. No idea what the optocouplers are as I am still a newbe in learning.

          Originally posted by Biruslapio View Post
          There are SMD resistors and optocouplers who also can fail when IGBTs short,on solder side,check all optocouplers for low resistances between pins,and 10 or 100 OHMs resistors,ceramic capacitors.

          Comment


            #6
            Re: LG 60PZ750 running hot and maldischarged

            Thanks for the correction Tom.
            Goldberg, what voltage do you read for -Vy?
            Willing to help but I'm no expert.

            Comment


              #7
              Re: LG 60PZ750 running hot and maldischarged

              I got an amazing deal....I think..Lol on a Siglent SDS1202X-E 2-Ch 200MHz Super Phosphor Oscilloscope. No idea on how to use it except for the basics. I will post a pic when I get back home on Sunday

              Originally posted by tom66 View Post
              Nice, show scope pics

              Comment


                #8
                Re: LG 60PZ750 running hot and maldischarged

                Don't know where would I find the test points ?
                Originally posted by dick_barton View Post
                Thanks for the correction Tom.
                Goldberg, what voltage do you read for -Vy?

                Comment


                  #9
                  Re: LG 60PZ750 running hot and maldischarged

                  Siglent is decent and having the phosphor mode (like the Rigol DS1054Z) is really useful, so nice job.

                  -Vy and Vsc are on Y-sustain
                  Vzbias is on Z-sustain.

                  Points should be marked...look around for them.
                  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


                    #10
                    Re: LG 60PZ750 running hot and maldischarged

                    Thanks Tom, below are my readings so far. I will hunt around for the
                    vy when i get home tomorrow.

                    VS 201.2
                    VA 55.07
                    5V 5.13
                    VSC 150V
                    VZBias 105.5


                    Originally posted by tom66 View Post
                    Siglent is decent and having the phosphor mode (like the Rigol DS1054Z) is really useful, so nice job.

                    -Vy and Vsc are on Y-sustain
                    Vzbias is on Z-sustain.

                    Points should be marked...look around for them.

                    Comment


                      #11
                      Re: LG 60PZ750 running hot and maldischarged

                      this is a repair that i did on a LG Z-SUS,the Y-SUS also had the same problem plus shorted IGBTs,the black 5 pin component is the optocoupler,it was shorted on the 3 pin side between colletor,base and emissor,10 OHM resistor was open and the ceramic cap was shorted,in your case they aren't otherwise the panel wouldn't light up,but an altered resistance can cause this.
                      Also you should first check all the voltages,bad -VY can surely cause this problem,it did red pixels on a TV i've repaired.
                      Attached Files

                      Comment


                        #12
                        Re: LG 60PZ750 running hot and maldischarged

                        I increased the VZB to 110v, all other readings were near perfect.

                        VS 201.2
                        VA 55.07
                        5V 5.13
                        VSC 150V
                        VZB 110.
                        Vy 178.1


                        Originally posted by tom66 View Post
                        Siglent is decent and having the phosphor mode (like the Rigol DS1054Z) is really useful, so nice job.

                        -Vy and Vsc are on Y-sustain
                        Vzbias is on Z-sustain.

                        Points should be marked...look around for them.

                        Comment


                          #13
                          Re: LG 60PZ750 running hot and maldischarged

                          Just an update. I verified the problem still exists within the ZSUS board because I tested it in another TV and within 10 min it started to look maldischarged. Anyone have more ideas. I have attached pictures of the board. Could it be the driver IC's causing this ? Is it possible to use my new oscilloscope to track down the problem ?

                          Originally posted by goldbird78 View Post
                          I increased the VZB to 110v, all other readings were near perfect.

                          VS 201.2
                          VA 55.07
                          5V 5.13
                          VSC 150V
                          VZB 110.
                          Vy 178.1
                          Attached Files
                          Last edited by goldbird78; 03-26-2018, 08:35 PM.

                          Comment


                            #14
                            Re: LG 60PZ750 running hot and maldischarged

                            Yes it would be possible to use your scope.
                            You could follow the same guide as before with the VS_DA used to trigger your scope then one probe on the Z-sus output;
                            Since it's a digital scope you can then hit STOP and take a picture (may even save to USB for you)
                            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


                              #15
                              Re: LG 60PZ750 running hot and maldischarged

                              Is the Zsus output the resister by the VZB test points ?
                              Originally posted by tom66 View Post
                              Yes it would be possible to use your scope.
                              You could follow the same guide as before with the VS_DA used to trigger your scope then one probe on the Z-sus output;
                              Since it's a digital scope you can then hit STOP and take a picture (may even save to USB for you)
                              Attached Files

                              Comment


                                #16
                                Re: LG 60PZ750 running hot and maldischarged

                                Z-sus output is on those white connectors on the right. You can probably find it on a capacitor by tracing the big copper area that connects to those connectors. Don't mix it up with the ground, though.
                                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


                                  #17
                                  Re: LG 60PZ750 running hot and maldischarged

                                  how does this look ?

                                  Originally posted by tom66 View Post
                                  Z-sus output is on those white connectors on the right. You can probably find it on a capacitor by tracing the big copper area that connects to those connectors. Don't mix it up with the ground, though.
                                  Attached Files

                                  Comment


                                    #18
                                    Re: LG 60PZ750 running hot and maldischarged

                                    Beauty!
                                    And that's a nice waveform too, that scope renders that Z-sus waveform perfectly.
                                    (Hmm...may have to consider a Siglent upgrade from my Rigol)

                                    From that, I can see your Z-sus waveform looks perfect. Could you zoom in on the "burst" section on the right of the screen so you can see the sus_up and sus_down parts more closely? (This is the part of the waveform moving from 0-200V at a high frequency. It is responsible for making the panel light up.)
                                    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


                                      #19
                                      Re: LG 60PZ750 running hot and maldischarged

                                      Thanks Tom......It is a weird one, when starting up cold the picture is perfect then as the TV warms up the screen gets maldischarged and it definitely the zsus board because when I swap it out into another TV the exact same thing happens. The attached scope and screen pictures are after the TV has been on for 20 min. It seems like a component on the board is overheating once the TV is on for 10-15 min.

                                      Originally posted by tom66 View Post
                                      Beauty!
                                      And that's a nice waveform too, that scope renders that Z-sus waveform perfectly.
                                      (Hmm...may have to consider a Siglent upgrade from my Rigol)

                                      From that, I can see your Z-sus waveform looks perfect. Could you zoom in on the "burst" section on the right of the screen so you can see the sus_up and sus_down parts more closely? (This is the part of the waveform moving from 0-200V at a high frequency. It is responsible for making the panel light up.)
                                      Attached Files

                                      Comment


                                        #20
                                        Re: LG 60PZ750 running hot and maldischarged

                                        Yeah - looks odd

                                        Can you try setting the panel on a fixed colour pattern so that the waveform doesn't change - you could use something like MS Paint

                                        Then observe the waveform and see if anything happens to it as the fault develops - a video of the waveform may help me here
                                        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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