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  • Author Author: jw0752
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The small challenges in life. Fixing a bad CFL

jw0752

The Compact Flourescent Light or more commonly a CFL. For some time I have been popping open the ones that go bad and salvaging the board components.

 

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This one stopped making light but I could see that the small filament heaters at the two ends of the tube were still working. I opened it up by putting a screw driver in the seam of the plastic base and twisting. If you try this be sure to use some good leather gloves. If you do not at some point the driver will slip and you will stab your hand and be angry that you did not take my advice.  Here is what the insides look like:

 

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Each bulb usually contains the same components; a couple of inductors, 6 diodes, a trigger diode, a high voltage 22 uF electrolytic, a 1:1:1 high frequency transformer, 2 NPN transistors and several capacitors and resistors. I began my search for the problem by checking the transistors and diodes. I had to take the transistor out as it had an unusual base to emitter connection. After checking several other similar transistors and finding a consistent reading I put the it back into the circuit. In a short period of time I found a 2.7 nF 1200V Mylar with a dead short. The capacitor was replaced and the bulb was reassembled. This is the first time I have been able to repair a CFL. I should be unhappy that my time now is worth so little but it was fun and I am happy anytime I can fix something that is not suppose to be fixable.

 

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John

  • in reply to DAB

    other than to meet the average use times.

    That comment sparked me to check the life expectancy.

    Compare: LED Lights vs CFL vs Incandescent Lighting Chart

     

     

    The site above suggests 8000 hrs but I see an electrolytic capacitor buried amongst the components.

    Many of these are 1-2000 hrs.

    This is usually at the rated temperature, but many of the ones I looked at didn't have some form of temp/life chart.

     

    This is usually the component that fails in an LCD monitor, and a $20 fix plus some desoldering, etc.

     

     

    I guess it would be interesting to see where in the schematic it was, but the clue might be the base-emitter short.

    Perhaps there was a voltage spike and it sacrificed itself and protected the transistor ...?? image

     

     

    Regardless it's a great post and some additional information that only engineers would be interested in.

    Thanks John.

  • Great post John.

     

    I am not totally surprised that the component failed.

     

    All of these devices are planned for toss away, so there is little emphasis on quality other than to meet the average use times.

     

    Good work.

     

    DAB

  • in reply to jw0752

    Easy fix ...

    We all understand the test jig, but we're all aware that electricity and safety aren't foremost for others.

     

    I understood it was also powered by your isolation transformer, so therefore you'd need to get both leads for it to be unsafe image

     

     

    What surprises me is how little is holding the two halves together.

    I would have though you'd need more than a simple twist, and it would destroy getting it back together.

     

    Cheers

    Mark

     

     

    image

  • in reply to mcb1

    Thanks for your correct observation about the test jig. I let expediency get ahead of better judgement in posing the bulb for the picture. This site is generally pretty good about not portraying a cavalier attitude towards mains power thanks in large part to your vigilance. Thank you for this.

     

    John

  • Amazing that a simple cap died and took out what is supposed to be a long life lamp.

     

    Not sure we should be seeing the connection to power it though ... image