LG 32LS4600 no power

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  • synapse
    Senior Member
    • Jun 2012
    • 51
    • Australia
    #1

    LG 32LS4600 no power

    One day my wife went to watch TV when it went BANG!

    I haven't plugged it in since but on the weekend I pulled the back off to take a look at the power supply. The Fuse closest to the power plug is blown.
    I have check all diodes and resistors while in circuit (not ideal), none are shorted or open.

    Is there anything else I should check before replacing the fuse?
    I was at least thinking of replacing the samyoung capacitors to help it live a bit longer.
    Attached Files
    I'm currently a Part-time Computer Systems Engineering student.
    Full time Service Assurance (faults) for a large Telco.
    Tags: None
    • vinceroger69
      Badcaps Legend
      • Mar 2012
      • 6714
      • uk
      #2
      Re: LG 32LS4600 no power

      have you tested the bridge rectifier bottom right of first picture.

        Comment

        • synapse
          Senior Member
          • Jun 2012
          • 51
          • Australia
          #3
          Re: LG 32LS4600 no power

          You mean the bottom left? Yes that seems to be fine 0.57v on the diode test
          I'm currently a Part-time Computer Systems Engineering student.
          Full time Service Assurance (faults) for a large Telco.

            Comment

            • vinceroger69
              Badcaps Legend
              • Mar 2012
              • 6714
              • uk
              #4
              Re: LG 32LS4600 no power

              yes thats the one sorry i got left and right mixed up also next to the mains fuse there sa device hidden by shrink wrap tube does that test ok? also maybe if you havnt got one already build your self a dim bulb tester that way it will save you blowing fuses and any new parts etc.
              Last edited by vinceroger69; 11-07-2016, 06:48 AM.

                Comment

                • diif
                  Badcaps Legend
                  • Feb 2014
                  • 6978
                  • England
                  #5
                  Re: LG 32LS4600 no power

                  There should be more than one diode measurement when testing a bridge rectifier.
                  Is the thermistor ok ? it might just be the photo. Next to the fuse marked TH101.

                    Comment

                    • synapse
                      Senior Member
                      • Jun 2012
                      • 51
                      • Australia
                      #6
                      Re: LG 32LS4600 no power

                      Thank you both for replying.

                      Yeah there were multiple measurements for the bridge rectifier, both measured 0.57v on the diode test on pins 1 and 2, then the same for 3 and 4. Reversing the polarity gives me OL.

                      I'll check out the thermistor when I get home tonight. It looks like the easiest way to test will be to take a reading at room temperature, then heat it up and compare the readings?

                      I think i'll be making a dim bulb tester (I'll get multiple uses out of it I think)
                      I'm currently a Part-time Computer Systems Engineering student.
                      Full time Service Assurance (faults) for a large Telco.

                        Comment

                        • diif
                          Badcaps Legend
                          • Feb 2014
                          • 6978
                          • England
                          #7
                          Re: LG 32LS4600 no power

                          There's four diodes to check in the bridge rectifier.
                          Check the thermistor visibly (mine was cracked) and it's not shorted.

                          They were the two failed items in a similar power supply I repaired.

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA
                              #8
                              Re: LG 32LS4600 no power

                              What resistance do you get reading between the two outer pins (pin 1 and 4) of the bridge?
                              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

                                • synapse
                                  Senior Member
                                  • Jun 2012
                                  • 51
                                  • Australia
                                  #9
                                  Re: LG 32LS4600 no power

                                  Originally posted by budm
                                  What resistance do you get reading between the two outer pins (pin 1 and 4) of the bridge?
                                  This may be because it's in circuit, but I sometimes get a reading of 175k ohm and sometimes it's 7M ohm. Sometimes it starts out at 1 or 2M ohm and climbs up to 7M over about 10 seconds or so?
                                  I'm currently a Part-time Computer Systems Engineering student.
                                  Full time Service Assurance (faults) for a large Telco.

                                    Comment

                                    • synapse
                                      Senior Member
                                      • Jun 2012
                                      • 51
                                      • Australia
                                      #10
                                      Re: LG 32LS4600 no power

                                      Originally posted by diif
                                      There's four diodes to check in the bridge rectifier.
                                      Check the thermistor visibly (mine was cracked) and it's not shorted.

                                      They were the two failed items in a similar power supply I repaired.
                                      Both the thermistor and varistor near the #1 fuse seem ok, they are not open and not shorted (thermistor is in spec according to its data sheet)
                                      I'm currently a Part-time Computer Systems Engineering student.
                                      Full time Service Assurance (faults) for a large Telco.

                                        Comment

                                        • synapse
                                          Senior Member
                                          • Jun 2012
                                          • 51
                                          • Australia
                                          #11
                                          Re: LG 32LS4600 no power

                                          OK I found the issue.
                                          A hairline crack that opened right up once i bent it a bit.
                                          I'll replace this and the fuse and re-test.
                                          Attached Files
                                          I'm currently a Part-time Computer Systems Engineering student.
                                          Full time Service Assurance (faults) for a large Telco.

                                            Comment

                                            • synapse
                                              Senior Member
                                              • Jun 2012
                                              • 51
                                              • Australia
                                              #12
                                              Re: LG 32LS4600 no power

                                              Took a while to get the parts but replacing the fuse and the ceramic capacitor did the trick.
                                              I also rigged up a dim bulb tester, so that will come handy in the future!

                                              Thank you everyone for your help.
                                              Attached Files
                                              Last edited by synapse; 11-22-2016, 06:49 AM.
                                              I'm currently a Part-time Computer Systems Engineering student.
                                              Full time Service Assurance (faults) for a large Telco.

                                                Comment

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