Why does an LCD need a reset line?

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  • gabiz_ro
    Senior Member
    • Mar 2011
    • 166
    • Romania

    #21
    Re: Why does an LCD need a reset line?

    Or maybe CPU doesn't reach stage when LCD must be on so reset line is low.

    Comment

    • caphair
      Badcaps Legend
      • Nov 2011
      • 1249

      #22
      Re: Why does an LCD need a reset line?

      Originally posted by gabiz_ro
      Or maybe CPU doesn't reach stage when LCD must be on so reset line is low.
      What stage?

      Comment

      • gabiz_ro
        Senior Member
        • Mar 2011
        • 166
        • Romania

        #23
        Re: Why does an LCD need a reset line?

        So if this line is shorted then it's the transistor within the CPU that's gone bad holding it at 0v correct?
        I mean power up,resume from standby etc.

        Are you sure is shorted?
        In many cases when you measure something like that on powered devices is possible that multimeter read in fact C-E or G-S (depending on transistor used) in ON state.
        Is more convenient to keep reset low and timed enabled as needed vs let it floated or high and just a pulse when needed.That for devices in stand-by or sleep mode.

        Without battery or charger connected is still short on that line?

        Comment

        • caphair
          Badcaps Legend
          • Nov 2011
          • 1249

          #24
          Re: Why does an LCD need a reset line?

          Yes I measured with no power at all in diode mode, red probe on ground and black probe on the reset pin and get 0v.

          A known good working board with same measurement done in diode mode reads .432v

          Not sure how it shorted or why

          Comment

          • gabiz_ro
            Senior Member
            • Mar 2011
            • 166
            • Romania

            #25
            Re: Why does an LCD need a reset line?

            Is clear now that is a short on this line.
            I suppose LCD was disconnectet too.
            Can't look on schematics if there are any other components,like a capacitor,from this to ground.
            Just fixed few days ago on 6s draining battery and can't enable touch id.
            One little capacitor get shorted.

            Comment

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