TV not powering on - with standby red –led flashing

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  • Willem01
    Member
    • Feb 2021
    • 45
    • South africa

    #41
    Re: TV not powering on - with standby red –led flashing

    Looks like you are right about the short circuite
    Attached Files

    Comment

    • Willem01
      Member
      • Feb 2021
      • 45
      • South africa

      #42
      Re: TV not powering on - with standby red –led flashing

      Originally posted by dick_barton
      Either the gate/ source of the mosfet is short circuit or more likely the zener diode ZD3.
      You need to lift off ZD3 and make a note of which way around any markers are so it goes back in the exact same position. Then check its resistance when out of circuit.

      Can you post a photo of that area so I can see the components mentioned.

      R30 looks as though its a 100 ohm resistor so I think D10 is probably damaged as well

      I would double check the mosfet as shown in many Youtube videos for example
      https://www.youtube.com/watch?v=gloikp9t2dA
      I have removed it form the board, do I just measure it on the ohm setting of the multimeter?

      Comment

      • dick_barton
        Badcaps Legend
        • Aug 2015
        • 6642
        • Wales

        #43
        Re: TV not powering on - with standby red –led flashing

        You can set your multimeter to ohms. If it's short circuit then it will read 0 ohms or close to 0 ohms
        Willing to help but I'm no expert.

        Comment

        • Willem01
          Member
          • Feb 2021
          • 45
          • South africa

          #44
          Re: TV not powering on - with standby red –led flashing

          Originally posted by dick_barton
          You can set your multimeter to ohms. If it's short circuit then it will read 0 ohms or close to 0 ohms
          OK so it is shorted,,,I cant get the same flatpin type, we only have the through hole kind with the same voltage spec. can I use that by trimming the wire so that it would fit on the board

          Comment

          • dick_barton
            Badcaps Legend
            • Aug 2015
            • 6642
            • Wales

            #45
            Re: TV not powering on - with standby red –led flashing

            If it fits without shorting out to the chassis when soldered in then it should be OK. What about the other components in the list. Have you checked them?
            Willing to help but I'm no expert.

            Comment

            • Willem01
              Member
              • Feb 2021
              • 45
              • South africa

              #46
              Re: TV not powering on - with standby red –led flashing

              Originally posted by dick_barton
              If it fits without shorting out to the chassis when soldered in then it should be OK. What about the other components in the list. Have you checked them?
              Oraait, the z-diode has been replaced and I have power to the board again, luckily that was the only part I needed to replace. All voltages on CON3 are in spec and the backlihgt led's are powering up.

              I still have one issue though, with the tv powered off and in standby mode after 5 minutes the led is not flashing, but when I push the power on button the led start flashing and doesnt come on.

              I did the following to test the standby power that is stored in the caps:
              I unplug the power cord from the tv, and still the the standby led is on I push the power-on button and the led goes out - this draining the standby power to power on the mainboard.

              To determine which cap is responsible for the standby power to be available. I plugged the power cord back into the tv with the standby led flashing, keeping an eye on it I heated each cap individually with a hair dryer and unplugging the power cord and pushing the power-on button again until I found which cap is the one - and it is C45.

              By reading the diagram C45 must be a 820uf10v cap, the cap that I have removed from the board was rated at 470uf10v.

              After all the caps was replaced the electronic shop gave me a 470uf16v cap for C45, would this be the issue with the cap that is out of spec that it still would not give power to wake up from standby mode.

              Only if I heat it up with the hair dryer on C45 it works 100% - how do I resolve this

              Comment

              • dick_barton
                Badcaps Legend
                • Aug 2015
                • 6642
                • Wales

                #47
                Re: TV not powering on - with standby red –led flashing

                Are there any components on the opposite side to C45 which may be heating up as you heat up C45. Is C30 in circuit? if so I would check that.
                Did you check the diode D15. Also check all the soder joints. Post a picture of the replacement capacitor. Ensure it's soldered in the correct way around.
                Willing to help but I'm no expert.

                Comment

                • Willem01
                  Member
                  • Feb 2021
                  • 45
                  • South africa

                  #48
                  Re: TV not powering on - with standby red –led flashing

                  I have placed a piece of cardboard in between the caps to prevent the heat-flow to each of the other caps, I test it 3 times every time I heat up C43 the led goes solid. I can see C30 is not in circuit

                  C45 is that blue cap

                  Then on D10 I did measure it and there was a ohm reading cant remember now as the board is mounted again in its place.
                  Attached Files

                  Comment

                  • dick_barton
                    Badcaps Legend
                    • Aug 2015
                    • 6642
                    • Wales

                    #49
                    Re: TV not powering on - with standby red –led flashing

                    The view from the top of C45 doesn't give a lot of information. Can you post all that is wriiten on it.

                    Are you saying you're losing the 3.3V supply when the set is in standby ?
                    What voltage do you have on L1 link when in standby?
                    Last edited by dick_barton; 03-06-2021, 01:15 PM.
                    Willing to help but I'm no expert.

                    Comment

                    • nomoresonys
                      Badcaps Legend
                      • Jan 2013
                      • 12086
                      • U.S.

                      #50
                      Re: TV not powering on - with standby red –led flashing

                      "470uf16v cap" Those specs are not a problem but you may just have a bad cap there.

                      Comment

                      • Willem01
                        Member
                        • Feb 2021
                        • 45
                        • South africa

                        #51
                        Re: TV not powering on - with standby red –led flashing

                        C45 blue one, must I replaced it with another one
                        Attached Files
                        Last edited by Willem01; 03-06-2021, 01:19 PM.

                        Comment

                        • dick_barton
                          Badcaps Legend
                          • Aug 2015
                          • 6642
                          • Wales

                          #52
                          Re: TV not powering on - with standby red –led flashing

                          No, It should be fine. Checking it was in correctly.
                          I think you are losing the voltage to U4 which is why the 3.3V is dropping. It would be interesting to see what voltage is on D9 cathode and whether it does drop in standby.
                          Willing to help but I'm no expert.

                          Comment

                          • Willem01
                            Member
                            • Feb 2021
                            • 45
                            • South africa

                            #53
                            Re: TV not powering on - with standby red –led flashing

                            Originally posted by dick_barton
                            No, It should be fine. Checking it was in correctly.
                            I think you are losing the voltage to U4 which is why the 3.3V is dropping. It would be interesting to see what voltage is on D9 cathode and whether it does drop in standby.
                            For the heck of me, where do you find those components,,been looking and looking but not getting it

                            ....
                            OK found the buggers you are referring to...how do I go about to measure to answer your Q
                            Last edited by Willem01; 03-06-2021, 01:43 PM.

                            Comment

                            • dick_barton
                              Badcaps Legend
                              • Aug 2015
                              • 6642
                              • Wales

                              #54
                              Re: TV not powering on - with standby red –led flashing

                              Here we are as per your photo
                              Attached Files
                              Willing to help but I'm no expert.

                              Comment

                              • nomoresonys
                                Badcaps Legend
                                • Jan 2013
                                • 12086
                                • U.S.

                                #55
                                Re: TV not powering on - with standby red –led flashing

                                An easy way to partially test a cap in circuit is to set your meter to 20k ohms and put a meter lead on each leg of the cap and see if it goes up steadily or down steadily, can test one nearby to compare if they are acting the same. As always be careful not to touch capacitors leads with your hands as they can carry a DEADLY CHARGE, that one shouldn't as it's 16v but the big ones do.
                                Last edited by nomoresonys; 03-06-2021, 07:14 PM.

                                Comment

                                • Willem01
                                  Member
                                  • Feb 2021
                                  • 45
                                  • South africa

                                  #56
                                  Re: TV not powering on - with standby red –led flashing

                                  I tried to resimulate the heating of the blue cap,, its not tbat one.
                                  I isolated C18, C19, C20 heated them with the hair dryer and the standby led came to a solid on state and the tv powers up.
                                  Remember I replaced all the caps except C1 and C2
                                  Is there something in circuite I can check why when I heat them up it opens the 3.3v standby power
                                  Last edited by Willem01; 03-07-2021, 01:54 AM.

                                  Comment

                                  • dick_barton
                                    Badcaps Legend
                                    • Aug 2015
                                    • 6642
                                    • Wales

                                    #57
                                    Re: TV not powering on - with standby red –led flashing

                                    Are you saying you're losing the 3.3V supply when the set is in standby ?
                                    What voltage do you have on L1 link when in standby?
                                    I think you are losing the voltage to U4 which is why the 3.3V is dropping. It would be interesting to see what voltage is on D9 cathode and whether it does drop in standby.
                                    What is the answer to the above questions?
                                    Willing to help but I'm no expert.

                                    Comment

                                    • nomoresonys
                                      Badcaps Legend
                                      • Jan 2013
                                      • 12086
                                      • U.S.

                                      #58
                                      Re: TV not powering on - with standby red –led flashing

                                      Make sure C45 is not in backwards.

                                      Comment

                                      • Willem01
                                        Member
                                        • Feb 2021
                                        • 45
                                        • South africa

                                        #59
                                        Re: TV not powering on - with standby red –led flashing

                                        Originally posted by dick_barton
                                        What is the answer to the above questions?

                                        On L1 it fluctuates 3.6 - 4.7 with the standby led flashing
                                        When I unplug the CON3 plug for 10 sec plug it back the led stops flashing amd turn solid, then the volt on L1 is about 22v
                                        D9 cathode voltage fluctuates from 21v - 60v that is without any pins jumped
                                        Attached Files
                                        Last edited by Willem01; 03-08-2021, 05:36 AM.

                                        Comment

                                        • Willem01
                                          Member
                                          • Feb 2021
                                          • 45
                                          • South africa

                                          #60
                                          Re: TV not powering on - with standby red –led flashing

                                          Originally posted by nomoresonys
                                          Make sure C45 is not in backwards.
                                          See post #51 image

                                          Comment

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