Sharp LC-50LE442u will only go one once - sometimes

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  • mwend
    Member
    • Mar 2009
    • 12
    • USA
    #1

    Sharp LC-50LE442u will only go one once - sometimes

    I have a Sharp LC-50LE442u that I can get to work once...

    Well after reading up on suggestions here, discharging the caps, and holding the input/vol Dn buttons while plugging the unit, after about 10 sec release the buttons. The stand-by light is solid red. Pressing the remote power on button will turn the TV on and the stand-by light goes green. TV seems to work fine at this point, tested with TV Menu, HDMI and VGA/3.5mm audio.

    Problem is when the TV is turned off. Press the Power button on the remote and the TV goes off and the Stand-by light goes red (as expected).
    The TV will then not turn on after that, no video and no sound, but stand-by light does go to Green. At this point the power button does not seem to do anything, Stand-by light stays Green but no video and no audio

    I've tested the remote power button and console push. Both have the same effect. No Video and no sound and stand-by light stays green.

    All CAPs "look" OK. I've removed a few CAPs from the MainBoard for ESR testing all tested good.

    I've voltage tested the power board and got some interesting results. There is no schematic and no board "labels" on what the voltage lines are. I can only use the wire color as identifiers.

    ** After performing the above to make the TV work,
    Standy light is green, TV working
    ++ TV turned back on, after turning it off, Standby light is green, no video, no audio
    Color TV on ( v)** TV Off (v) Turn on Again (v)++
    Navy .03 .04 .04
    Green .88 .02 3.3
    Purple 3.3 .03 .06
    Yellow 3.3 .02 3.3
    Red 5.3 5.4 5.3
    Red 5.3 5.4 5.3
    Red 5.3 5.4 5.3
    Black 0 0 0
    Black 0 0 0
    Orange 12.1 0 12.1
    Orange 12.1 0 12.1
    Orange 12.1 0 12.1
    Black 0 0 0
    Black 0 0 0
    Black 0 0 0


    Is this a Power supply board issue or a main board issue? Suggestions?
    Attached Files
    PC XT, overclocked to 10 Mhz, with 8-bit expansion BUS, 640KB RAM and dual 5.25" floppies
    Tags: None
    • Andrew F. Ali
      Badcaps Legend
      • Jan 2014
      • 2450
      • Trinidad & Tobago
      #2
      Re: Sharp LC-50LE442u will only go one once - sometimes

      Seems to me that you have 5V St-By from PSU. Getting BL-ON signal, but not getting Pwr-ON signal from the Main Bd. Cold solder joints probably or e-caps ESR high on the Main Bd. Inspect the PSU for cold solder joints, too.

        Comment

        • dick_barton
          Badcaps Legend
          • Aug 2015
          • 6642
          • Wales
          #3
          Re: Sharp LC-50LE442u will only go one once - sometimes

          There's a thread here with a similar problem

          https://www.badcaps.net/forum/showthread.php?t=46046
          Willing to help but I'm no expert.

            Comment

            • Andrew F. Ali
              Badcaps Legend
              • Jan 2014
              • 2450
              • Trinidad & Tobago
              #4
              Re: Sharp LC-50LE442u will only go one once - sometimes

              Originally posted by dick_barton
              there's a thread here with a similar problem

              https://www.badcaps.net/forum/showthread.php?t=46046
              +1

                Comment

                • mwend
                  Member
                  • Mar 2009
                  • 12
                  • USA
                  #5
                  Re: Sharp LC-50LE442u will only go one once - sometimes

                  Wow, that was fast. Thank you for the ideas. I will be removing those CAPs tonight and checking/replacing them. Hopefully I will be able to read the sides for the values and I hope I have some on hand. I'll admit, I did pass over the PSU, particularly the Primary side when I noticed I had, what seemed to be the proper voltage at secondary connector.
                  PC XT, overclocked to 10 Mhz, with 8-bit expansion BUS, 640KB RAM and dual 5.25" floppies

                    Comment

                    • mwend
                      Member
                      • Mar 2009
                      • 12
                      • USA
                      #6
                      Re: Sharp LC-50LE442u will only go one once - sometimes

                      The 4 small CAPs seem ok. - I was hoping they were bad.

                      https://www.badcaps.net/forum/showthread.php?t=46046

                      Removed and tested the 4 small CAPs. Qty 3 - 10 uF 50v and Qty 1 - 4.7 uF 50v
                      All tested via ESR meter 10.3, 10.10, 10.15 , 4.77 . Similar readings with my DMM uF and Ohm readings OK. (the black stuff feels like silicon and cuts easily with a knife)

                      I'm up for more ideas.
                      PC XT, overclocked to 10 Mhz, with 8-bit expansion BUS, 640KB RAM and dual 5.25" floppies

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA
                          #7
                          Re: Sharp LC-50LE442u will only go one once - sometimes

                          So what are the result of the ESR value for those caps? You only posted the Capacitance readings of the 4 caps.
                          "Similar readings with my DMM uF and Ohm readings OK" What do you mean by the Ohm reading OK?
                          Last edited by budm; 11-15-2016, 10:47 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

                            • mwend
                              Member
                              • Mar 2009
                              • 12
                              • USA
                              #8
                              Re: Sharp LC-50LE442u will only go one once - sometimes

                              Ok here are the values I measured for the 4 small CAPS
                              Qty 3 - 10 uF 50v and Qty 1 - 4.7 uF 50v

                              Cap uF, ESR(Ohm) Vloss
                              10.3, 1.6, 0.9%
                              10.1, 1.5, 1.0%
                              10.2, 1.5, 0.9%
                              4.8, 2.4, 0.5%

                              These are Su'scon HG caps ( double checked this HG on all)
                              The specs are listed herehttp://www.su-scon.com/Templates/att/HG.pdf?lng=en
                              but I cannot seem to find either the 4.7 or the 10 on these pages.
                              To me the values look to be on par with the specs on the last page, but I could be wrong on that. More eyes could certainly help.
                              Thoughts or this or anything else here.

                              For what its worth, I have a whole set of CAPs plus some extras on order from mouser.
                              PC XT, overclocked to 10 Mhz, with 8-bit expansion BUS, 640KB RAM and dual 5.25" floppies

                                Comment

                                • mwend
                                  Member
                                  • Mar 2009
                                  • 12
                                  • USA
                                  #9
                                  Re: Sharp LC-50LE442u will only go one once - sometimes

                                  Just a follow up on my issue here and information for all...

                                  Solved: My power supply board (PSU) was just fine all along.
                                  The issue was solved with a replacement main board as shown here

                                  https://www.badcaps.net/forum/attach...4&d=1479092391

                                  Thanks for the assistance.
                                  ..On to the next project
                                  PC XT, overclocked to 10 Mhz, with 8-bit expansion BUS, 640KB RAM and dual 5.25" floppies

                                    Comment

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