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Sharp LC- 58Q620U - Standby Light, No Backlights or Image

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    #1

    Sharp LC- 58Q620U - Standby Light, No Backlights or Image

    Hello, I have a Sharp LC- 58Q620U 58" LED 4K TV.

    When you initially plug the TV into the 120V outlet, I get the initial standby red LED light. After you press the power button the red LED goes out and no other lights come. There is no backlight flash, nor image on screen. No audio with HDMI source plugged in, nor does my laptop detect another monitor plugged in. T-con board makes a clicking sound with or without LVDS cables hookup or off.

    My first thought was that it had a faulty PSU. Reading voltages, I was getting a swinging voltages from the DC output from the bridge rectifier onward.
    Replaced the PSU with a brand new unit. Getting very similar symptoms.

    PSU# RSAG7.820.8349/ROH (REPLACED WITH NEW, HAD SAME SYMPTOMS)

    MAINBOARD # RSAG7.820.8353/ROH

    ( Readings with ** are voltages that are swinging or fluctuating every second or so)

    Bridge Rectifier- 120.8v ac / 161.1v dc – 167.7v dc **

    Cap1 (C810) – 349.1v | Cap2 (C811) – 349.2v

    Before Pressing Power Button ( Standby Light LED ON )
    BSW .039v | TSW 0v (pin1)
    PWM .030v | PWM 0v
    GND 0v | VAMP 19.85v Falling
    GND 0v | VAMP 19.9v Falling
    NC 0.041v | GND 0v
    GND 0v | STB 0.073v
    12V 9.04v - 9.30v ** | 12V 9.05v to 9.3v **
    3D5G 0v | 12V 9.04v - 9.29v **

    After Pressing Power Button ( Standby OFF - No Other LEDS Lit )

    After Pressing Power Button
    BSW 4.667v - 4.679v ** | TSW .004v (pin1)
    PWM 2.025v - 2.054** | PWM 0v
    GND 0v | VAMP 19.97v - 20.16v **
    GND 0v | VAMP 19.98v - 20.15v **
    NC .110v -.152v ** | GND 0v
    GND 0v | STB 2.708v - 2.712v **
    12V 9.88v - 12.14v ** | 12V 10.2v - 12.14v **
    3D5G 0v | 12V 10.18v - 12.14v **

    I have not been able to dig up a schematic or service manual for the TV or Boards

    Hopefully, I have given enough information for it to be useful.

    EDIT - Failed to mention, this model does not have any volume or channel buttons on the unit itself. Only a single power / rocker button on the bottom right of TV.
    Attached Files
    Last edited by Tecc1229; 09-17-2021, 10:57 AM.
    Tags: None
    #2
    Re: Sharp LC- 58Q620U - Standby Light, No Backlights or Image

    Most of these 58” tvs are the same even though different manufacturers names are on them.

    Usually it’s the backlights. And on some models it blows a mosfet on the power supply as well.

    Start there first by checking voltages on the power supply.

    Comment

      #3
      Re: Sharp LC- 58Q620U - Standby Light, No Backlights or Image

      Update: Due to the high amount of reported LED failures on these TV's, I decided to finish tearing it down. The Backlight power line did not show open. Tested each LED and did find a faulty LED.
      Replaced the faulty LED and the TV is not operational again. I am going to order a full LED replacement set.
      Reassembled and did find a single purple vertical line on the picture. Progress at least.
      Before LED replacement, the main board would not boot up and the T-Con was clicking, indicated a power fault and cycle. No more T-con click and full picture.

      Comment

        #4
        Re: Sharp LC- 58Q620U - Standby Light, No Backlights or Image

        Well, the Single vertical line turned into the TV no longer booting up. Backlights still running.

        Turning the TV on, the standby light will flash 20 times and stop.

        Unplugged the left LVDS and the TV boots up and displays like normal with right only running. T-con failure or panel failure? Ideas?

        Comment

          #5
          Re: Sharp LC- 58Q620U - Standby Light, No Backlights or Image

          Sounds like panel issue if it works with 1 side of the lvds unplugged.

          Check for shorted caps on the panel driver board. If non you can try the tape method and see if that works.

          Comment

            #6
            Re: Sharp LC- 58Q620U - Standby Light, No Backlights or Image

            UPDATE:

            Replaced the T-Con board. Now I have full image and picture. I do have a single red vertical line. I suspect panel board short or damage.

            I am going to explore taping off the clock lines to isolate the issue. Anyone happen to have a schematic for either the panel or T-Con board?

            Comment

              #7
              Re: Sharp LC- 58Q620U - Standby Light, No Backlights or Image

              A single red vertical line is most likely a bad panel, or more precisely the COF is defective and that column is kept in a constant on state. You will likely have to live with it or part the TV out.

              Comment

                #8
                Re: Sharp LC- 58Q620U - Standby Light, No Backlights or Image

                I agree. I am going to explore a bit more and see what I can come up with. At this point, why not. Its a learning experience

                I am attaching the Data Sheet for the panel itself. In case it becomes useful for someone else.
                Attached Files

                Comment

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