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820-2936-B does not turn backlight

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  • 820-2936-B does not turn backlight

    hello have a 820-2936-B does not turn backlight, measurements have taken are:
    F9700 = 12v
    PP3V3_S0 = 3.26v
    PPBUS_SW_BKL = 11.94v
    PP5V_S0 = 4.98v
    PPBUS_SW_LCDBKLT_PWR = 0.04v wrong. After 30 seconds of setting up to 2.25V unstable
    Q9706 PIN 3 8.05v.

  • #2
    Q9706 is being told to turn on. What is on pin 4 and what is on pin 6?

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    • #3
      Originally posted by dukefawks View Post
      Q9706 is being told to turn on. What is on pin 4 and what is on pin 6?
      Sorry Q9706 PIN 1: 0.02v 30 sec Powering unstable. 1.82v PIN 3: 8.05V 30 sec Powering unstable. 12.7V PIN 4: 12V.
      Last edited by willie; 09-21-2016, 03:53 PM.

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      • #4
        When there is 8V on pin 3 and 12V on pin 4 there should be 12V on pin 1. Looks like a bad Q9706 to start with, but check that LCD_BKLT_EN is high.

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        • #5
          Originally posted by dukefawks View Post
          When there is 8V on pin 3 and 12V on pin 4 there should be 12V on pin 1. Looks like a bad Q9706 to start with, but check that LCD_BKLT_EN is high.
          there is a problem here. In Q9707 pin 2 2.29v pin 6 0.95V pin 4 0v (pin 5 0v LCD_BKLT_EN) pin 3 8.52v.

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          • #6
            If LCD_BKL_EN is not there do you even have an image on the LCD? Check with a flashlight.

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            • #7
              if you have the screen image. what it is the backlight turns on the screen.

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              • #8
                Check LCD_BKL_EN again, it must be there. Check resistance to GND too on there.

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