Burned resistor, what value ?

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  • diif
    Badcaps Legend
    • Feb 2014
    • 6978
    • England

    #1

    Burned resistor, what value ?

    I open my friends dead fan and find a burned resistor.
    Looks like black black ? Gold
    The burned band I think is either grey or black, so to me that suggests 0 ohms. Was it used as a fuse ?
    Thoughts please ?
    Attached Files
  • eccerr0r
    Solder Sloth
    • Nov 2012
    • 8701
    • USA

    #2
    Re: Burned resistor, what value ?

    Maybe brown black silver gold, but this resistance is a bit low as a guess as to what the original resistance would be.

    This looks like a capacitive dropper power supply, so yes it was mostly used as a fuse.

    What's the uF of the yellow capacitor, and what is this controlling (cant be the actual fan motor? Relay somewhere? How big of a relay?)
    Last edited by eccerr0r; 03-20-2018, 10:40 AM.

    Comment

    • Andrew F. Ali
      Badcaps Legend
      • Jan 2014
      • 2450
      • Trinidad & Tobago

      #3
      Re: Burned resistor, what value ?

      Looks like a 1ohm 2Watt resistor

      Comment

      • diif
        Badcaps Legend
        • Feb 2014
        • 6978
        • England

        #4
        Re: Burned resistor, what value ?

        Thanks eccerr0r. The yellow capacitor top left is 0.1uf, the larger one bottom middle is 0.33uf both X2
        The connector top right has three wires that go into the fan, I doubt the relay is inside. It's 230V 21-33W.
        The IC is an Atmel Mega48pa.

        Comment

        • eccerr0r
          Solder Sloth
          • Nov 2012
          • 8701
          • USA

          #5
          Re: Burned resistor, what value ?

          Yes I would also think it should be in the ohms range (gold multiplier band) and not tenths of ohms range (silver multiplier band) because of the capacitive dropper circuit. The third band looks silver-ish.

          The "bottom middle" I think what you mean / 0.33uF capacitor is what I was curious about - this is the dropper capacitor. A 0.1Ξ© resistor might make sense with a 1uF dropper but agree with Andrew that it should be higher than this, mainly due to it being pointless being that low for a 0.33uF.

          Comment

          • diif
            Badcaps Legend
            • Feb 2014
            • 6978
            • England

            #6
            Re: Burned resistor, what value ?

            Thanks, I've stuck in a 0.33 ohm 2watt resistor as it's the closest I have in stock.
            Fan now powers on.

            I think I have discovered the reason it burnt. He had connected it to one of those cheap dimmer plugs https://www.amazon.co.uk/Dimmer-Adju.../dp/B01G1WEKW4 and turned it down for the first time yesterday.

            Looking at the fan instructions, that's not how it wants controlling.

            Comment

            • Andrew F. Ali
              Badcaps Legend
              • Jan 2014
              • 2450
              • Trinidad & Tobago

              #7
              Re: Burned resistor, what value ?

              Good work!!!.....

              Comment

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