LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

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  • slappala
    Member
    • Nov 2011
    • 44

    #41
    Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

    Originally posted by tom66
    Same here. No idea how it fixes it but it does. Seems very common with LG plasmas.
    I guess U702 monitors the AC primary's two sides with these optocouplers.

    When the 3-4 pins are joined the U702 thinks the AC is on all the time by circulating the 5.v signal back to the IC. Basically thinks the opto is on state what it really is also except during the 200ms at the start where the opto ON signal would be lost sometimes.

    Yep, something wrong with the optos or the AC primary waveform at the start..TV works now again without hickups so before some PSU components fail completely I will just use it like it is

    Comment

    • tom66
      EVs Rule
      • Apr 2011
      • 32560
      • UK

      #42
      Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

      Originally posted by slappala
      I guess U702 monitors the AC primary's two sides with these optocouplers.

      When the 3-4 pins are joined the U702 thinks the AC is on all the time by circulating the 5.v signal back to the IC. Basically thinks the opto is on state what it really is also except during the 200ms at the start where the opto ON signal would be lost sometimes.

      Yep, something wrong with the optos or the AC primary waveform at the start..TV works now again without hickups so before some PSU components fail completely I will just use it like it is
      I figure the same. Pins 3 and 4 make the optocoupler seem always on. It might be the PFC bus caps aging or the TL431s being damaged. (These sensed the voltage on the primary on my model.)
      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

      • MoDu
        New Member
        • Jan 2013
        • 4
        • Portugal

        #43
        Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

        How long have you had this "hack" force tv to not auto-shutdown?

        I've had all the problems described here, even went as far as replacing all big caps and even a whole YSUS board, but alas, it remained the same.

        I shorted out the suggested pins on the opto-couplers and so far so good.

        Will this kill my tv in a few months? Or will it just keep going until a fuse or a IC burns?

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK

          #44
          Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

          I had it running for a month, but sold the TV on after that due to the LG "sparklies" issue.

          The only disadvantage that I can see is the audio doesn't mute on power off, so you'll get a loud crackling sound. This is a common phenomenon with audio amplifiers. Some can detect the failure of their supply voltage and mute immediately, whereas others require an external signal. AC detect provides this signal, along with the signal to the processor to tell it to keep running.
          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

          • MoDu
            New Member
            • Jan 2013
            • 4
            • Portugal

            #45
            Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

            Audio is a non issue for me, I don't use the TV's audio at all.

            I was able to easily fix the sparklies with some tinkering on the Var resistors, they're now invisible at a regular viewing distance.

            So my only concern right now is whether this will destroy what's left of the Z board.
            Last edited by MoDu; 01-15-2013, 04:11 PM.

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #46
              Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

              I doubt it will do any damage to the sustain boards. My 42" actually ran for half a second with this bridge made, you could see picture slowly fade out before it cut out completely, so it does shut down reasonably cleanly.

              The speakers will make click noise even if nothing normally comes out of them, so to avoid this simply unplug the speaker connector on the AV board (board with SCART etc on it.)
              Last edited by tom66; 01-15-2013, 04:08 PM.
              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

              • MoDu
                New Member
                • Jan 2013
                • 4
                • Portugal

                #47
                Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                Thanks for the tips.

                Comment

                • MoDu
                  New Member
                  • Jan 2013
                  • 4
                  • Portugal

                  #48
                  Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                  I tried turning on the sound, to see if I could hear the speaker thump you mentioned, but it was barely noticeable. It only happens when I unplug the cord, simulating a power outage.

                  BTW, disabling the speakers in the menu is enough to NOT have this side-effect.

                  Comment

                  • tom66
                    EVs Rule
                    • Apr 2011
                    • 32560
                    • UK

                    #49
                    Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                    Great, so there is no issue. Yes, it only happened on mine when power is unplugged, and only then on bright scenes. Dark scenes caused no click. I figured this was due to the standby supply lasting longer than the main supply so the TV could recognise a power failure and cut off the speakers.
                    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

                    • er_rusty
                      New Member
                      • Jul 2013
                      • 3
                      • Spain

                      #50
                      Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                      Originally posted by tom66
                      Okay, pin 4 on the optocouplers is on the phototransistor side.

                      They're the only signals coming FROM the primary to the secondary, normally the signals go to the primary side from the secondary.

                      Need a closer pic of under these devices.

                      You will probably need to place a solder bridge between pins 4-3 on both optocouplers. That's how I fixed mine.
                      Hi to all!! I'm new, I have a LG 42PC1RV-ZJ plasma TV that had the same symptoms slappala TV. I think that the solution can be the same.

                      Please, i don't understand very well what i have to do:
                      Maybe I have to place a solder bridge between pins 4 of one optocoupler to pin3 on the other???
                      Or I have to put a solder bridge between pin 4 of a optocoupler to pin 3 on the same in booth optocoupler?


                      TOM66 help me please!

                      Thanks a lot!!

                      Comment

                      • tom66
                        EVs Rule
                        • Apr 2011
                        • 32560
                        • UK

                        #51
                        Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                        Pin 4-3 on BOTH optocouplers. i.e. 2nd choice.

                        Only bridge the devices which have 4-3 on the SECONDARY (isolated side.) Do NOT bridge them on the primary.
                        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

                        • er_rusty
                          New Member
                          • Jul 2013
                          • 3
                          • Spain

                          #52
                          Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                          Originally posted by tom66
                          Pin 4-3 on BOTH optocouplers. i.e. 2nd choice.

                          Only bridge the devices which have 4-3 on the SECONDARY (isolated side.) Do NOT bridge them on the primary.
                          Thank you!

                          Comment

                          • benfinland
                            Member
                            • Jul 2013
                            • 20
                            • Finland

                            #53
                            Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                            What are these optocouplers? And where? I was wondering about bridging them to see if the tv will fire up

                            Comment

                            • tom66
                              EVs Rule
                              • Apr 2011
                              • 32560
                              • UK

                              #54
                              Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                              Not relevant to your model unfortunately.
                              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

                              • er_rusty
                                New Member
                                • Jul 2013
                                • 3
                                • Spain

                                #55
                                Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                                Originally posted by tom66
                                Pin 4-3 on BOTH optocouplers. i.e. 2nd choice.

                                Only bridge the devices which have 4-3 on the SECONDARY (isolated side.) Do NOT bridge them on the primary.
                                It works!!
                                Thank you again!!

                                Comment

                                • tom66
                                  EVs Rule
                                  • Apr 2011
                                  • 32560
                                  • UK

                                  #56
                                  Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                                  This has to be the tenth TV with this issue so far fixed. Glad to hear, enjoy your TV!
                                  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

                                  • Shipmaker
                                    Member
                                    • Feb 2014
                                    • 36
                                    • Germany

                                    #57
                                    Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                                    Hallo everybody I m new on this board!

                                    Thank you for your solution, because i v got the exactly same powersupply in
                                    my LG42PC1RV and in nobody could help me, but now!
                                    I also recogniced while I looking tv that a little green snow apperes, to see
                                    in black parts of tv picture and while changing programm.

                                    But my Question is : How do you bridge with solder or with a wire?

                                    (Please, forgive me my bad english, i am german)
                                    Thanks!

                                    Comment

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

                                      #58
                                      Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                                      You can bridge the opto with blobs of solder done carefully this is fine.
                                      --But,--As Tom says--Only bridge the one side of the optos.

                                      The green spots can be adjusted out sometimes but the official cure is a Software Update to the Contol-Board.
                                      --Let me know if you want control-board update, I have the complete kit to update lots of LG sets--including the PC1 series....
                                      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

                                      • Shipmaker
                                        Member
                                        • Feb 2014
                                        • 36
                                        • Germany

                                        #59
                                        Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                                        Thank you for the fast reply,

                                        now i try out to fix my tv with an solder bridge!

                                        I dont now if this kind of Modell LG 42 PC 1 RV is able to update on software side
                                        but i will take a look on my service manuall and tell you if it s possible.

                                        But again Thanks a lot!

                                        Comment

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

                                          #60
                                          Re: LG 42PC3RA SMPS power_ysus problems on/off/on click and fixes

                                          According to my data--its updateable, Its the Control-Board firmware that needs doing, not the mainboard or the set itself.

                                          Tell me the numbers written on the back of the banel metal-work, be something like 42X3####
                                          Last edited by Alastair E; 02-15-2014, 12:51 PM.
                                          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

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