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How to test CCFL ?

Discussion in 'General Electronics Discussion' started by mikey5791, Dec 8, 2014.

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  1. mikey5791


    Jun 7, 2013
    Dear all,

    I recently acquired a pair of CCFL (backlight tube) from a damaged Sharp 10.5 inch LCD Display Screen Model LQ15x14. One of the backlight tube with pink and white wire is seen from img 0647 as attached.

    I wish to use an inverter for CCFL (img 0646) to light up the backlight tube.
    The description on the inverter is input:12V DC, output:900V 50HZ, Lamp: 300mm
    It seems the 12V DC input wire is red and black, the output is white wire with black cap plastic socket.
    I am wondering which side of the white wire should go to either the pink or white wire of the CCFL and whether is it ok to use this inverter to light the CCFL?

    Any advice and suggestions are appreciated. Many thanks in advance.

    Attached Files:



    Sep 23, 2012
    A CCFL (Cold cathode Fluorescent Lamp) is just like any other tube fluorescent lamp. It's a tube with a small amount of mercury, Current limited High voltage AC is applied to ionize the mercury gas which when ionized produces UV light. The UV light causes the coating on the bulb to glow. The modern consumer incadescent replacement CCFL's usually have the inverter built into the base of the bulb. Those used in monitors and TV's require external inverters.

    I know your looking for answers and not guess' but, my approach would just try different connections and see. I don't believe the ccfl is polarity sensitive, The output of your inverter is AC.

    I have a high voltage inductive wand made by Millwaukee for testing standard flourescent (T-12) etc bulbs. I tried making a direct connection to the pink and then white wire and it didn't illuminate. The wand needs to be actually touching the bulb itself, the:wires cause too much loss.

    I'm liking your little supply, I'm guessing it will work, 900V seems about right for LCD backlite monitors per tech spec.

    Let us know how your inverter works, and where you got it. I'd like to buy one of the same if it works for you.
    Last edited by a moderator: Dec 18, 2014
  3. mikey5791


    Jun 7, 2013
    Hi Y2KEDDIE,

    Your explanation on CCFL is informative and helpful. As the ccfl is not polarity
    sensitive, I connected the pink and white ccfl wire to inverter output then feed the inverter input to 12V DC battery supply as image attached. Voila, there is light from the bulb and tested IMG_0684-lights.JPG for about 1 minute, meaning the salvaged ccfl bulb is still good.

    Back to your question, I bought the ccfl inverter from an electronic store in Taichung,Taiwan while on vacation last year, The inverter is sold for Taiwan dollar 70 (equivalent to about 2.25 US dollar). Not too sure though if this can be bought online but it works for me as a ccfl bulb tester.

    Thanks again for the suggestion and good tips.
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