Multimeter LCD Display not working

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  • tmhobadcap
    Senior Member
    • Apr 2019
    • 146
    • CANADA
    #1

    Multimeter LCD Display not working

    I have a Sanwa CD-720C multimeter. Recently, it is not working. There is no display when it is turn on. But when I use the continuity test, it still can produce sound when the two leads are touching each other. Therefore, I suspect it is just the display not working. I have checked that the fuse is okay. What will be the possible cause? Can it be fixed?
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    • redwire
      Badcaps Legend
      • Dec 2010
      • 3906
      • Canada
      #2
      Re: Multimeter LCD Display not working

      I would give the board a good clean with IPA and an old toothbrush. Some of the IC pins 13,16,18,20,21 looks like solder specs or something bridging things?

      The DMM IC is custom for Sanwa SAD8701 but it must use a charge-pump for the LCD voltage boost. I would check the four tantalums "AJ6". there should be more than 3V on at least two.

      This guy took his apart: https://getitonrecord.weebly.com/202...er-repair.html

        Comment

        • tmhobadcap
          Senior Member
          • Apr 2019
          • 146
          • CANADA
          #3
          Re: Multimeter LCD Display not working

          Originally posted by redwire
          I would give the board a good clean with IPA and an old toothbrush. Some of the IC pins 13,16,18,20,21 looks like solder specs or something bridging things?

          The DMM IC is custom for Sanwa SAD8701 but it must use a charge-pump for the LCD voltage boost. I would check the four tantalums "AJ6". there should be more than 3V on at least two.

          This guy took his apart: https://getitonrecord.weebly.com/202...er-repair.html
          After cleaning the board with alcohol as you suggested, the meter works again. Thanks a lot.

            Comment

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