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CFL Bulb Repair

By on February 27, 2015










Yesterday evening when I switched “ON” CFL Bulb (compact fluorescent lamp) in my house passage I observed the bulb is glowing half the way.

cfl bulb

So I have removed it from the socket and opened the unit to repair it.


On visual inspection I did not found any physical damage. As per my previous experience I have checked the capacitor marked on PCB circuit as a “C3” which is coupling the filaments of bulb please see the circuit diagram for reference tips

 cfl bulbs

I have removed the C3 capacitor from the PCB and on testing it with my multimeter I found the capacitor was shorted.


But problem is that this type of capacitor is not available in open market and buying it online is not worth hence I have made a habit if equipment is not repairable due to any reason I always salvage the parts or full PCB for future repairing use. In this case I managed to find the part from junk board.

compact fluorescent lamp

After replacement of the capacitor I have re fixed the cfl lamp and take a look at the result below:

compact fluorescent bulbs

This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.

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  1. ricardo ramos

    February 27, 2015 at 6:52 pm

    Excellent job Yogesh. Thank you for sharing this important tips.
    May you continue to share with us more good tips.

  2. reza

    February 27, 2015 at 8:45 pm

    when read, i use this article .
    thank u

  3. Robert Calk

    February 27, 2015 at 8:45 pm

    Thanks for sharing your article. Sir, how did you check the capacitor to find out that it was shorted, and why didn't you take a picture of it so we could see? Sir, are you sure it didn't just have a bad solder joint?

  4. Humberto

    February 27, 2015 at 9:22 pm

    Good job Yogesh, that capacitor is very problematic. I have many PCBs stored in my place to get some electronic components, that's a good idea.

  5. Corriete

    February 28, 2015 at 6:56 am

    wonderfully done! thanks for sharing this with me,surely enjoyed this

  6. venugopal rao

    February 28, 2015 at 11:21 am

    Excellent article by Yogesh. I am following all of your articles. very useful and informative.

  7. sayed

    February 28, 2015 at 3:30 pm

    thank you for sharing your expriments

  8. dicksy

    February 28, 2015 at 3:31 pm

    thanx yogesh.

  9. Abdul Haleem

    March 1, 2015 at 1:19 am

    No Robert Calk, The subject capacitor give up (becomes shorted) for the reason we don't know. I too have faced similar trouble with many CFL bulbs irrespective of brands. We need to find the same valued replacement. Higher than 2.7nF or 3.9nF capacitors won't work.

    • Robert Calk

      March 1, 2015 at 9:56 pm

      I was just wondering why he didn't have a picture with the cap on the meter showing that it was shorted. If it were my article, there would be a picture so everybody could see the cap was indeed shorted. I believe that the reason is because it was just a bad solder joint and not a bad cap.

  10. Marijus Brikas

    March 1, 2015 at 2:07 am

    Actually, it is a very common cfl bulb fault. I've repeared lots of them (just haven't thought this could be worth a good article). Instead of polyester capacitors I use high voltage ceramic disc capacitor, of capacity between 1 to 3.3 nF (in most cases they are colored in blue). These are available in most radioelectronics shops. Smaler capacity I use when it is not enough space for bigger one. I am not sure, that they are really performing in this circuit as good as polyester one, but no one has failed during period of many years. Ane they are more resistant for electric break down.

  11. Gary Gemmell

    March 1, 2015 at 10:20 am

    Great idea i always strip old pcb's for parts and store them and they always come in handy eventually.

    Pity we live in a throwaway society where even a bulb like that is thrown in the bin. Well done Yogi!!!

  12. Ehsan Murad

    March 1, 2015 at 11:45 am

    Thanks you Yogesh.I would also like to know how you came to know capacitor is shorted.

  13. Augis

    March 1, 2015 at 1:13 pm

    The lamp symbol in schematics is wrong - where are the filaments you are talking about?

  14. Yogesh Panchal

    March 1, 2015 at 10:01 pm

    Dear all ,

    Thanks for your comments and suggestions,I have already mentioned in this article about i have found this capacitor shorted while tested with multimeter and also i have mentioned i have checked directly this capacitor as per my previous experience.(i Have tested each components out of the PCB on my first experience because that time i am not aware of circuit diagram of cfl)this is common problem in this type of symptom in CFL Bulbs.
    Any way the process of fault finding: The bulb working half of the way that means lack of voltage to CFL filament; now desolder the filament from the PCB Test the filament resistance anything between 10 to 200 Ohm if OK that menace CFL filament is working fine, also check the tube for physically damage.(the Best way to test the CFL Tube is replace it with working CFL if you have one in your junk box) now test the component one by one reverse way on PCB from filament and find the culprit.

  15. Marijus Brikas

    March 2, 2015 at 1:01 am

    In most cases You do not need to check capacitor directly.
    first, if the circuit looks good (fuse can be blown), there is a need to check bulb filaments. Both should have resistance of about 10 ohm or similar. If everythong is ok, the only bad component remains capacitor.
    Sometimes short capacitor can not be found using simple multimeter (as measuring voltage is in the range of few hundreds milivolts), so insulation meter can be used, or any other continuity circuit, with voktage of few tenths of volt.

  16. Vasile Petrica

    March 2, 2015 at 3:05 am

    I apreciated your article!Bravo,bravo.

  17. Pete Singh

    March 11, 2015 at 9:03 pm

    Yogesh you the man dude keep up the good work sharing your knowledge with others is the best experience .


    May 7, 2015 at 8:05 pm


  19. Goutam Praharaj

    August 4, 2016 at 8:36 pm

    What is the specification of F1


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