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Sharp LC-70LE745U

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    #21
    Re: Sharp LC-70LE745U

    Update: just to test out the main I plugged in the bluray and I am getting sound . I only get image with the flashlight

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      #22
      Re: Sharp LC-70LE745U

      As I am just learning was hoping someone with more knowledge would jump in so we could further this repair along and I could further my education
      I assume no responsibility for any stupid suggestions I might post.

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        #23
        Re: Sharp LC-70LE745U

        Then I could only suggest that the BL-ON section of the Main Bd may be faulty but the other sections are OK. Though I do not think the PSU is defective as you replaced it with a 'known' working Bd and the result was the same. Here is a little trick to further rule out the PSU Bd and indeed the Backlight power supply section.
        With the backlights connected:
        1. WRT chassis GND check the voltage on the two LED +ve pins of the LED jack. If the voltage goes high and then drops to 50-75% of the correct voltage, then you can assume the LEDs supply power is OK This could also indicate a shorted Backlight LED in the chain. We could rule this out as EACH individual LED was checked.
        2. WRT chassis GND check the voltage on the two LED -ve pins of the LED jack. Normally they should be 4-10V. If they are open or 0V, then we could assume the Backlight LEDs are open and need to be replaced. We could rule this out as EACH individual LED was checked.
        3. WRT chassis GND if the LED -ve pins are high about 30V this would indicate an open LED Driver on the PSU. Connect one end of a100 ohm resistor to chassis GND and the other end to the high LED -ve pin and apply power. If the LED backlights turn ON then you can be sure you have a defective PSU/ LED Driver circuit.

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          #24
          Re: Sharp LC-70LE745U

          STB pin is the BL-ON pin.
          You are not getting PWM dimming (PWM1, PWM2) control signals and the analog dimmer is showing 0.7V which is also low but I do not believe the analog dimming is being used.
          What is the LCD panel model number?
          Right now the boost converter is not running.
          You LED tester shows Vf of 92V so the boost converter should be putting out over 100V. No PWM = no booster.
          Last edited by budm; 08-02-2017, 01:08 AM.
          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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            #25
            Re: Sharp LC-70LE745U

            So, what was the solution? I got exactly the same issue. Thx

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              #26
              Re: Sharp LC-70LE745U

              Check pin 21 ofl, meter in vdc mode, neg probe on metal chassis ground, pos probe on pin 21, check with tv plugged in but off [standby] leave meter probes where they are power up tv, what voltages do you have both in standby and after power up and are they steady? go ahead and check all the pins.
              Last edited by nomoresonys; 09-14-2022, 10:44 AM.

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                #27
                Re: Sharp LC-70LE745U

                if your backlights are not coming on, can try to power on the powerboard as stand alone, involves UNPLUGGING cable from powerboard to mainboard, leave it off, use four 1k resistors to jump ps-on, ofl, pwm1, pwm2, jump those 4 pins to bu5v, plug power cord into powerboard, plug into outlet, see if backlights come on and stay on.

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                  #28
                  Re: Sharp LC-70LE745U

                  If LED's are good, try to get into service menu, search for code.
                  If TV comes up, I think the error code needs to be reset, then TV should work ok.

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                    #29
                    Re: Sharp LC-70LE745U

                    exactly as AlfaTv says.. search the service manual for these operations..

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                      #30
                      Re: Sharp LC-70LE745U

                      try this: on tv button board, hold volume down and input, keep holding while you plug the tv in, hold them til tv comes on, se if you have a K on the screen then hold volume down and channel down, service menu should pop up, MUST be very CAREFUL in service menu, something done wrong can brick your tv, you want to clear your lamp errors if you have any, use remote if you can, use channel down, keep going til you get to lamp error reset, use volume up and volume down to adjust, so volume up to turn it on, then do channel up to reset, turn it on with volume button just like before, then go channel up to industry init. enable that then push ok or enter key on remote, wait a bit see if screen changes colors, if it does go ahead and unplug tv, wait a minute, now hold power button on tv while plugging tv in, you can let go when you see the indicator light on front light up, give it a while it should go to the initial setup, remember be VERY CAREFUL in the service menu, maybe take pictures or write settings down befroe you change any so maybe you can go back to previous settings if needed.

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