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eax55357701 repair

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    #21
    Re: eax55357701 repair

    should I bench test it with load on 12V & 20V outputs ?

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      #22
      Re: eax55357701 repair

      Compare all the diodes and resistors from both boards, as in check D501 on one board and the other, see if any are different, sometimes not all, you get fluctuating voltages with bad voltage regulating diodes or bad solder joints on transformers or elsewhere.
      Last edited by nomoresonys; 10-18-2019, 10:15 AM.

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        #23
        Re: eax55357701 repair

        It is either the PS-ON is fluctuating or the VCC that is generated by the standby power supply power transformer AUX winding is fluctuating that is why the PFC Voltage on the main caps and the 12/20V are fluctuating.
        Verify that the PS-ON is constant, if it is then check the VCC Voltage of the PFC IC and the 12/20V SMPS IC. May be the filter caps for the VCC from AUX winding are bad.
        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

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          #24
          Re: eax55357701 repair

          ps_on does cycle every 3 secs after you push on/off button.
          +5V is steady
          +12V cycles every 3 seconds 0 - 12.2V
          +20V cycles every 3 secs 0 - 21.33V

          I've checked both boards - ohming out resistors. checked caps. checked diodes. I'll check again tomorrow

          The LM431 to-92 did fix the as431 that were bad. This shunted regulator should have been a higher rated part. The SMD is only 0.28 watt where the to-92 pkg is 0.8 watt

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            #25
            Re: eax55357701 repair

            Right now you have PS-ON issue. You need to run the power supply board by itself and connect 1K resistor between PS-ON pin and the standby power supply output to force on the power supply manually and see if the PRC and the switched power supplies are steady or not.
            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


              #26
              Re: eax55357701 repair

              thats exactly what I was thinking. i try that tomorrow morning. since I replaced the 2 as431 - it is acting differently.

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                #27
                Re: eax55357701 repair

                bench testing PSB: PS_on jumpered with 1K to +5V gives
                +12V is 12.3V
                +20v is 19.64V
                PRC is 0V

                PSB stays on - does not cycle

                I replaced the AS431 with new LM431 TO-92 pkg on the working board and it still works perfectly
                Last edited by ajshoe; 10-20-2019, 09:59 AM.

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                  #28
                  Re: eax55357701 repair

                  was using the wrong ground for PFC - it holds steady at 386V along with the other voltages.
                  so bench testing both PSB shows voltages:

                  lbl Good board non-working board

                  +5V +5.14V +5.1V
                  +12V +12.28V +12.30V
                  +20V +19.6V +19.63V
                  PFC +380.2V +385V

                  I've going to give up on this - seems like its either a PSB current problem or some sort of over protection circuit.
                  Last edited by ajshoe; 10-21-2019, 07:45 AM.

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