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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 jw0752

    About the same technology these days.... It could be  a good competition.. What can you make from the guts of a CFL bulb?!

  • in reply to mcb1

    Yeah those components are highly stressed inside of a CFL and rarely do they get near the expected lifetime.

    Hacking them open you can get access to a good source of high voltage components..at least some of them should be in good nick!

  • in reply to jw0752

    John

    Good advice about the gloves, I'm sure someone will fail to read it.! image

     

    The transistor used in this model is a D128PL

    You could try 2SD128PL.

    Not uncommon for japanese makers to drop the 2S from the front.

     

    I've never subscribed to CFL's.

    My house has Dichroic with suitable beam angle and wattage to suit the requirement, but I do understand some places with recessed fittings where there is little light spill and require 4,6 or even 8 in a medium sixed room.

     

    Mark

  • in reply to DAB

    I had to laugh as I used to work on $30,000 x-ray units and now I am specializing in $2 light bulbs.

    John

  • in reply to mcb1

    Hi Mark,

    They aren't all the same with regards to separating. This is one of the better ones. The hard ones it becomes much more important to have a good pair of gloves on when trying to work the screw driver into the crack.

     

    You have a good memory to remember that I work the 120 on my bench off an isolation transformer. You are correct it take two leads to tango in this situation but your cropped replacement photo eliminates any misunderstandings.

     

    The units have the 22 uF electrolytics but I have yet to find one of these failed or damaged. The transistor used in this model is a D128PL which I have not been able to cross reference but the transistor tester shows it as an NPN with a built in flyback diode. There is considerable heat near the circuit board as there is visual evidence of carbonization of the circuit board particularly near the transistors.

     

    John