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Festive/Christmas LED lights

  • 02-03-2019 8:43pm
    Registered Users Posts: 41 Darcon

    More of a curiosity question because most people will probably say "bin them!"

    I have a set of festive/Christmas tree lights (100 in the string). It is possible to string several of these lights in a daisy chain. Hence, there is a (two pin) plug at one end and a (two pin) socket at the other end.

    The rating says 100 lamps at 3.5V, 0.07 W. The light set has a 7W rating.

    The original AC/DC converter does not work.

    Thus, using an AC/DC transformer (which can output between about 3V and 12V in switchable steps), I connect the set and test at various voltages between 3.5V and 12V DC and changing the polarity each time. The lights do not light up.

    Now the strange thing is that if I test for electrical continuity between either pin of the plug at one end of the string and either pin of the socket at the other end, I get electrical continuity for each of the pins. Why? Or put it another way, if there is electrical continuity, why don't the LEDs light when connected to the transformer?