LG 42LD490 stuck in standby with flashing red light

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  • Ady2017
    Senior Member
    • Dec 2017
    • 50
    • UK
    #1

    LG 42LD490 stuck in standby with flashing red light

    The problem with my TV is very similar to an earlier post but there was no final solution posted.

    When the TV is first turned on from cold it will not turn on. The red standby light begins pulsing and a high pitch whine is heard. The back light remains off. If the TV is left trying to boot like this and then turned off and on again a few times then eventually it will turn on and sit there working all day long.

    I initially suspected the PSU after spotting this kit for sale,
    http://www.ohmsupplies.co.uk/epages/...roducts/KIT229

    The capacitors generally look ok and I have however tried swapping a few of them out just in case but it has made no difference. The only thing left would be to swap all the capacitors just in case one is bad but not bulged or leaking etc.

    I have now been reading a lot of posts saying the main board is the likely culprit. I have had the main board in the over before at 200 degrees for 10 mins to fix it stuck with the spinning logo and it has been perfect since.

    Is there a way to fully test the PSU before throwing money at it potentially unnecessarily changing all the capacitors?
    Tags: None
    • Ady2017
      Senior Member
      • Dec 2017
      • 50
      • UK
      #2
      Re: LG 42LD490 stuck in standby with flashing red light

      Update - I have just been around the back of the TV and tried to listed where the high pitch sound is coming from which it makes while trying to start up. It is definitely coming from the main board and not the PSU board and so I guess that is the most likely culprit then.

      It looks like the place selling a capacitor kit for the PSU to fix the problem is misleading.

        Comment

        • vinceroger69
          Badcaps Legend
          • Mar 2012
          • 6714
          • uk
          #3
          Re: LG 42LD490 stuck in standby with flashing red light

          you could try heating the power supply up with a hair dryer for a few minutes does the tv start up now if ok its possible the capacitors are bad high esr etc ohms supplies are a good company i have brought a lot of parts from them.

            Comment

            • Ady2017
              Senior Member
              • Dec 2017
              • 50
              • UK
              #4
              Re: LG 42LD490 stuck in standby with flashing red light

              Yes, that seems like a great idea as whatever component it is that is faulty it does not like being cold. Try warming up the PSU first and if not then try warming up the suspect IC on the main board. It is one of those challenging intermittent problems - the TV is on right now and is working perfect but nobody dare turn it off!

                Comment

                • vinceroger69
                  Badcaps Legend
                  • Mar 2012
                  • 6714
                  • uk
                  #5
                  Re: LG 42LD490 stuck in standby with flashing red light

                  On the lgs i have worked on expecially the older ones its 50/50 psu or main that was at fault if bad caps on psu the hair dryer trick usually works. if your doing more repairs maybe look into getting a tester like this
                  https://www.ebay.co.uk/itm/224157573...0AAOSwHuhfYHSL

                    Comment

                    • Ady2017
                      Senior Member
                      • Dec 2017
                      • 50
                      • UK
                      #6
                      Re: LG 42LD490 stuck in standby with flashing red light

                      Just thinking about it a bit more, it makes sense that it would be a main board issue as once the TV is on, it would happily keep working 24/7 until I switch it off and let it cool down. My bedroom TV on the other hand likes a new set of PSU caps every other year and the first sign of trouble is it keep switching itself off when it gets hot.

                      I have had a ESR meter on my list of things to buy for a while but I am a bit dubious about buying anything from ebay and especially being dispatched from China!
                      Last edited by Ady2017; 11-16-2021, 03:10 PM.

                        Comment

                        • dskall
                          Badcaps Legend
                          • Oct 2016
                          • 2905
                          • usa
                          #7
                          Re: LG 42LD490 stuck in standby with flashing red light

                          You could do the same with the mainboard. Heat different parts if not starting, or cool parts when it's working. Should be easy to narrow down.
                          I assume no responsibility for any stupid suggestions I might post.

                            Comment

                            • vinceroger69
                              Badcaps Legend
                              • Mar 2012
                              • 6714
                              • uk
                              #8
                              Re: LG 42LD490 stuck in standby with flashing red light

                              Originally posted by Ady2017
                              Just thinking about it a bit more, it makes sense that it would be a main board issue as once the TV is on, it would happily keep working 24/7 until I switch it off and let it cool down. My bedroom TV on the other hand likes a new set of PSU caps every other year and the first sign of trouble is it keep switching itself off when it gets hot.

                              I have had a ESR meter on my list of things to buy for a while but I am a bit dubious about buying anything from ebay and especially being dispatched from China!
                              The esr tester i linked above i brought from ebay and it came from china it works fine for what i need, you can also update the firmware on the tester too make it more acurate. I was looking at the peak atlas esr 70 which also is a good tester and can test in circuit.

                                Comment

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