Westinghouse A190E3-H01 no backlight / shutdown

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  • caphair
    Badcaps Legend
    • Nov 2011
    • 1249

    #21
    Re: Westinghouse A190E3-H01 no backlight / shutdown

    Originally posted by budm
    "Mosfet Ics I measure:
    S1-D1(Two D1 pins) 570ohms
    S2-D2(Two D2 pins) 530 ohms

    S1-D1(Two D1 pins) 570 ohms
    S2-D2(Two D2 pins) 529 ohms"

    Those are tested off the board and probe in both directions? There is body Diode on Source and Drain pin, so in one direction it should show as open circuit.
    In circuit and yes they show open in the opposite direction. When I had them out of circuit they tested the same, though I do not remember exact values.

    Comment

    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA

      #22
      Re: Westinghouse A190E3-H01 no backlight / shutdown

      That is fine then, we are looking for something <50 Ohms.
      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

      • caphair
        Badcaps Legend
        • Nov 2011
        • 1249

        #23
        Re: Westinghouse A190E3-H01 no backlight / shutdown

        When the backlights quickly flash, there's a very high pitched noise associated with them.

        Also the high pitch noise is present with the monitor off, then it stops when turned on and then heard louder with backlight's attempting to illuminate.

        So the transformers are fine? Am I wrong to have assumed there should be no reading between primary and secondary points?

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #24
          Re: Westinghouse A190E3-H01 no backlight / shutdown

          The inverter transformer high voltage winding has on end connected to the sensing circuits to detect if the lamp are connected or not or if the lamp does not stay on, it is not isolated circuit.
          "Also the high pitch noise is present with the monitor off, then it stops when turned on and then heard louder with backlight's attempting to illuminate." OK that is one of the important info. i thought it only squeals when you turn on the monitor.
          I would re-cap the board at this point, also check the solder joints, rectifier diodes on the secondary side of the power transformer, etc.
          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

          • caphair
            Badcaps Legend
            • Nov 2011
            • 1249

            #25
            Re: Westinghouse A190E3-H01 no backlight / shutdown

            Originally posted by budm
            The inverter transformer high voltage winding has on end connected to the sensing circuits to detect if the lamp are connected or not or if the lamp does not stay on, it is not isolated circuit.
            "Also the high pitch noise is present with the monitor off, then it stops when turned on and then heard louder with backlight's attempting to illuminate." OK that is one of the important info. i thought it only squeals when you turn on the monitor.
            I would re-cap the board at this point, also check the solder joints, rectifier diodes on the secondary side of the power transformer, etc.
            I tested the rectifier diodes and both tested short circuit on the outer two pins of the three. Is that normal? This is in circuit

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #26
              Re: Westinghouse A190E3-H01 no backlight / shutdown

              They are Common Cathode dual rectifiers, Center pin is the common Cathode, the two outer pins are Anode, they are connected in parallel (the two Anodes are tied together if look at the traces on the board) to form as one Diode for half wave rectifier circuit.
              You can also try heating up the board first with hair dryer for 2~3 minutes and then plug the monitor into the outlet and see if it will function.
              Last edited by budm; 12-18-2014, 04:41 PM.
              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

              • caphair
                Badcaps Legend
                • Nov 2011
                • 1249

                #27
                Re: Westinghouse A190E3-H01 no backlight / shutdown

                I tried heating all the secondary side capacitors with a heat gun for a minute and half, still same symptom.

                Comment

                • caphair
                  Badcaps Legend
                  • Nov 2011
                  • 1249

                  #28
                  Re: Westinghouse A190E3-H01 no backlight / shutdown

                  Recapped secondary side caps, still same hissing noise and symptoms

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #29
                    Re: Westinghouse A190E3-H01 no backlight / shutdown

                    There is a small startup cap (CE107?) in the primary side close to the big power transformer, try that one too.
                    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

                    • budm
                      Badcaps Legend
                      • Feb 2010
                      • 40746
                      • USA

                      #30
                      Re: Westinghouse A190E3-H01 no backlight / shutdown

                      Oh I also forget to ask what DC Voltage you get at the two legs of the main filter cap (120uF 400V) laying on its side.
                      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

                      • caphair
                        Badcaps Legend
                        • Nov 2011
                        • 1249

                        #31
                        Re: Westinghouse A190E3-H01 no backlight / shutdown

                        Originally posted by budm
                        Oh I also forget to ask what DC Voltage you get at the two legs of the main filter cap (120uF 400V) laying on its side.
                        I measure 170vdc in standby.

                        I'm trying to find spare capacitors to replace the little start up one.

                        Something to note, if I disconnect tcon the quick burst of backlights is way brighter but again same thing, quick flash doesn't stay on.

                        Comment

                        • caphair
                          Badcaps Legend
                          • Nov 2011
                          • 1249

                          #32
                          Re: Westinghouse A190E3-H01 no backlight / shutdown

                          Changed the start up cap, no change

                          Comment

                          • caphair
                            Badcaps Legend
                            • Nov 2011
                            • 1249

                            #33
                            Re: Westinghouse A190E3-H01 no backlight / shutdown

                            Ok I think there's an issue with one of the ccfls. I disconnected the pink/white cable one and plugged in the blue/white connector in its place and the screen flashed this. If I leave blue/white connector in place and just unplug pink/white I get no flash of backlights at all but you can see a "no signal" image
                            Attached Files

                            Comment

                            • caphair
                              Badcaps Legend
                              • Nov 2011
                              • 1249

                              #34
                              Re: Westinghouse A190E3-H01 no backlight / shutdown

                              Fixed. Turned out to be a bad connection at one of the CCFLs. Carefully soldered and it's up and running!

                              Comment

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #35
                                Re: Westinghouse A190E3-H01 no backlight / shutdown

                                Thanks for the follow-up. So the arcing you were hearing then is from the lamp as I suspected in the beginning of the thread?
                                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

                                • caphair
                                  Badcaps Legend
                                  • Nov 2011
                                  • 1249

                                  #36
                                  Re: Westinghouse A190E3-H01 no backlight / shutdown

                                  Originally posted by budm
                                  Thanks for the follow-up. So the arcing you were hearing then is from the lamp as I suspected in the beginning of the thread?
                                  It didn't sound like arcing just high frequency. I took panel apart and powered it on and the same noise was heard on the return lines from the ccfls so I figured I'd check the connections out and one of the wires just came apart when handling. Resoldered and all is good.

                                  Comment

                                  • budm
                                    Badcaps Legend
                                    • Feb 2010
                                    • 40746
                                    • USA

                                    #37
                                    Re: Westinghouse A190E3-H01 no backlight / shutdown

                                    If you plan to do more monitors repair, I would suggest you to make at lest two test lamps, it will save so much times on finding out if you have board problems or lamps problems.
                                    This one is really confusing too so make it hard to figure out where the problem is:
                                    "Also the high pitch noise is present with the monitor off, then it stops when turned on and then heard louder with backlight's attempting to illuminate."
                                    Last edited by budm; 12-21-2014, 02:42 PM.
                                    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

                                    • caphair
                                      Badcaps Legend
                                      • Nov 2011
                                      • 1249

                                      #38
                                      Re: Westinghouse A190E3-H01 no backlight / shutdown

                                      Originally posted by budm
                                      If you plan to do more monitors repair, I would suggest you to make at lest two test lamps, it will save so much times on finding out if you have board problems or lamps problems.
                                      This one is really confusing too so make it hard to figure out where the problem is:
                                      "Also the high pitch noise is present with the monitor off, then it stops when turned on and then heard louder with backlight's attempting to illuminate."
                                      Yes I'll have to find some spare lamps for future testing.

                                      Also what's strange is even with it fixed I still can hear the high pitch noise when it's off and then you can hear frequency of lamps while on. So idk about that

                                      Comment

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