Don't Miss

How To Repair CFL Bulb -Lesson Learnt

By on March 10, 2015











Some times ago I was able to help one of my friends who did small charity work by thinking differently. There is a free school for poor kids conducted by a temple close to his home. Having asked them to bring “burnt/removed” CFLs, he was able to collect about 67 bulbs after 3 month. Then we were able to fix about 46 out of 67 by following the tips I have discussed below. Then we handed over them to the school as a small gift. In my country the cost of a CFL is 4USD+, so we were able to save nearly 200USDs of that poor Kid’s fund. However we spent only about 7USDs for the entire task. (ex: 13001 transistor  = 0.04USD here).

Lesson Learnt:

 how to repair cfl bulb flickering

Generally, CFL comprise 2 part— CFL Glass and the Oscillator circuit. If the glass part is burnt or break, you can’t fix it unless you find a good glass-part from another one. 


However if the glass is good, the issue must be on the circuit—Great! If the complaint of the cfl light bulb is flickering, no light, dim light (dimmable problem) or light shutdown after few seconds you can start repairing it as I have described below. 95% guaranteed !!

 cfl  bulb repairing


Separate the CFL in to glass & circuit safely. Test the connectors of the Glass (Pic 2) with a Multimeter (Connectivity check). If it’s in a good condition you may see 20-40 ohm or hear the “shorted” beep from the DMM.  Both the pin-pairs must be good! If so then check the circuit.

 cfl bulb repair circuit

On the circuit the first thing you must check is the fuse. If it’s burnt, most probably rectifiers or switching transistors got shorted. 

1. Check all the rectifiers you can see on the PCB.  If you see a short circuit, it’s better you check it by removing it from the PCB, because in some designs, a Toroid is used. Due to it’s pin connectivity you may see surrounding components are shorted at your first glance.   

2. If all the rectifiers are good, then check 2 switching transistors by removing from the PCB. If you find any shorted rectifier or a transistor at this stage, just replace all of them. If not follow other steps.. 

 cfl bulbrepair

Sometimes “blown fuse” issue can be seen due to shorted Inductors. So check it with a “blue ring tester(Mr. Jestine Yong had discussed advantages of a blue ring tester many times. See my home made tester in Pic 4). If you can’t see no more than 2 LEDs or no LED at all, just replace it (You must see at least 3 LEDs for this kind of inductors). 

If you have checked everything up to now, but the CFL is still dead—check all the resistors with a DMM and replace if you find blown one. If there is no Fuse even in the original design, put one (1ohm 1/2W) between the AC input and the PCB. At the same time, check the “Choke” with a blue ring tester. This time you must see even one Green light! See pic 5)

However its rare to see “blown fuse” due to a faulty of the Choke, bust it cause “No light” commonly.


If you see very Dim light, light goes off after a few second or even no light at all, most probably C3 ceramic capacitor is shorted. So check it and replace with a similar one (see Pic 1 & 3). 

If you find that the light is low than early, CFL lamp takes a few seconds to come up when the switch is on, hear hum, Dim light or no light at all—Check the electrolytic Cap and replace it. (see Pic 1 & 3). 

Now you have checked all the main culprits. If you are still unable to find the rote cause, just check the remaining components such as ceramic caps. Check whether the copper tracks of the PCB is damaged, AC wire connectivity is good. 

If you see a DB3 Diac, please don’t bother on it. There is no chance to burn it. I haven’t found even one case with a faulty Diac. 

By now you have checked nearly everything of fixing the CFL, however if you still can’t locate it, please follow my “Secret-tip” below.

A Secret-tip!

If you have found all the parts including the switching transistors are good as I discussed, but still the light is dead-Just replace the 2 transistors with similar parts. Now you must get the light back—95% guaranteed!


Normally we check 2 transistors without applying the voltage on them. Then we see no leak between P-N gates. However switching transistors or Hi-voltage caps can be shorted (leak) only when hi-voltage and hi-frequency is applied on them. However we can’t identify this with a DMM during our regular testing process. So the only thing we can do is replacing them with new parts. 

** When replacing, please ensure E-C-B of the transistor, because I have seen 13001 transistors come with few different ping arrangements such as ECB, BCE..  if it’s a 14W or above one, if you can, replace 13001 with 13003 . 

Having followed above discussed points, I’m sure that you will be able to fix the lamp successfully. 

By the way if you want to learn how to cut open CFL lamp to repair or salvage the components you can click on the video below:


***Don’t forget about the disposal, dispose damaged Glass-parts properly, because mercury complexes inside them can cause hazards or problems to your life!!  










This article was prepared for you by Kushan Ranatunga who works as a Network Engineer in Sri Langka. He has been doing  electronic experiments since age 11.

Please give a support by clicking  on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.

P.S-  If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!


You may also check out the here CFL bulb repair by Yogesh.




  1. Merlin Marquardt

    March 10, 2015 at 11:01 pm

    Very nice. Good work.

    • mian

      August 3, 2015 at 10:22 pm

      I have gone through your article. I also repair energy savers. I share my views for the technicians/hobbiest. There are three stages of checking.
      Before opening the bulb, check the charging and discharging of Electrolytic Cap (meter should be at its lowest continuity range). If it is ok, then open the fitting and check the heating elements continuity. It both sides are ok, then thoroughly check the circuit i.e. burnt resistors, short diods / transistors. Very rare case, Diac is short. Better if you have a magnifying glass with you. Carefully check loose connections particularly main filter capacitor.
      If preopening bulb do not show charging/discharging, may be fuse is blown, or a resistor normally 1 ohm to 10 ohm in A/C series is blown, Electrolytic capacitor loose connection. Sometime with the passage of time its charging capability is very low or totally finished.

    • mian

      August 3, 2015 at 10:41 pm

      Sorry, I have missed one thing. Sometime choke is open. Please check the continuity.

    • Okeke Chukwuemeka

      May 28, 2019 at 6:44 am

      How and what is another name for the blue ring tester.
      How can I order/buy it from you sir.thanks

  2. Hiran

    March 10, 2015 at 11:41 pm

    Kushan lovely article, lam a total amateur but your article gave me a hell of a lead, l want to give you a small tip from my experience after playing around with cfl bulbs, to remove the casing without cutting, just spray the joint with WD40 and keep for a few minutes and tap the seam with a screw driver slowly and carefully, both pieces will come out clean without much effort, same is true if you want to open a mobile charger or a laptop power supply for repair without breaking or cutting. Enjoy.

    • Kushan

      March 11, 2015 at 2:00 pm

      Thanks Hiran, its a good point!

      • Amir Mukhtar

        March 12, 2015 at 12:48 am

        Mr. Kushan Ranatunga Thank you

        you did great work and Nice Sharing to Learners.

        Amir Mukhtar

  3. Yogesh Panchal

    March 10, 2015 at 11:57 pm


    Good explanation thanks for sharing.

  4. S Ramachandran

    March 11, 2015 at 12:23 am

    Good work and systematic approach . can you give the schematic of the home made Blue ring tester.

    • Kushan

      March 11, 2015 at 2:05 pm

      you can get it :,d.dGc&cad=rja

  5. Robert Calk

    March 11, 2015 at 3:23 am

    Nice article Kushan. You need to use an analog meter for checking transistors, or a Peak Atlas DCA 75 Pro if you can get one. But the analog meter is much better than a DMM for transistors and many other components.

    • Robert Calk

      March 11, 2015 at 3:26 am

      PS. Make sure the analog meter has X10 Ohms. It will have the added 9V battery, giving the meter 12 volts on X10.

      • Robert Calk

        March 11, 2015 at 10:26 am

        Only cowards click dislike all the time and don't identify themselves.

    • Kushan

      March 11, 2015 at 2:11 pm

      Thanks Calk!! i do use analog meters too and it's more reliable sometimes as you said. instead of Atlas DCA 75 Pro, i use the following item i bought from ebay's cheep and very good than i expected ...just try it if u can ...

      • Robert Calk

        March 14, 2015 at 11:41 am

        I'm curious as to why you didn't mention them in your article?
        You said that if the DMM didn't work we had no choice but to replace the transistors. Anyway, the little meter seems pretty good for the price, but I already have a DCA 75 Pro and love it very much.

  6. patrick mlengwe

    March 11, 2015 at 10:19 am

    Thank you for the article, I have tried and it works.

  7. Paresh

    March 11, 2015 at 11:02 am

    Very informative indeed! Thanks for the share.

  8. Muhammad Akhlaq

    March 11, 2015 at 11:18 am

    Well explained. Very much informative article. Keep it up.

  9. Ehsan Murad

    March 11, 2015 at 11:49 am

    Very educative article.Thank you.

  10. Gerald

    March 11, 2015 at 1:00 pm

    Hello Kushan,
    Great article, thanks for sharing. I started collecting those faulty CFL lamps a while ago and opening them and troubleshooting them, but not repairing them though. The reason for my curiosity is that a friend of mine was refused warranty exchange after two weeks while a ‘’5 years warranty’’ was printed on the box. The salesman told my friend that the lifetime would depend on how often we turn them on and off as the filaments would fail, like for a normal fluorescent bulb. I had serious doubts, hence my investigation and guess what… I still have to find out a burned filament. I don’t say that it doesn’t exist but it is certainly not the main reason of failure. Your article documents this fact perfectly. Most components seem to have failed because of heat or maybe poor quality components or both.
    Well done Kushan, a very nice and educative charity work.

    • Kushan

      March 12, 2015 at 12:52 pm

      Thanks Gerald! 🙂

  11. reza

    March 11, 2015 at 2:35 pm

    thank u
    very much.

  12. sarvjeet

    March 11, 2015 at 8:09 pm

    Thank you for sharing.
    I learned a lot from this article.can you provide the schematic of your blue ring tester.
    Thank you.

  13. Tito

    March 11, 2015 at 8:21 pm

    Kushan,this article is a real eye opener. Thanks for sharing. My worry,though,is that we have too much fake replacement component in my Malawi markets.

    • Robert Calk

      March 11, 2015 at 9:19 pm

      Hi Tito,

      All you need is Mr. Yong's e-book, " Testing Electronic Components", and an inexpensive analog meter with X10 Ohms that has the additional 9 Volt battery, and you will have no problem.

  14. Patrick Motley

    March 11, 2015 at 8:58 pm

    Great article! Is there an article on how to build a blue ring tester?


    March 12, 2015 at 12:09 am

    Hi Kushan.
    Thanks for sharing your valuable and systematic fault finding approach.if possible can you provide the schematics of blue ring tester?
    Thanking you in advance.

  16. Abdul Haleem

    March 12, 2015 at 12:14 am

    Perfect tips Kushan, instead of MJE1300X/E1300X family lower numbered transistors I prefer to 13007 to 13009 if the space on the PCB and our wallet permit. The higher the transistor part number the higher the voltage & current rating. I'm proud to be your compatriot. Although I do e-repair I'm unable document it and post on Jestine's.

    • Kushan

      March 12, 2015 at 1:03 pm

      Thanks bro;

      you are correct ! with high rated transistors you can definitely expect longer lifetime. even use 13003

  17. Amir Mukhtar

    March 12, 2015 at 12:46 am

    Thanks you Mr. Kushan Ranatunga to sharing very nice article on CFL Savor.
    Great Work and Allah Bless you . Aameen.

    keep Sharing

    Amir Mukhtar AShrafi

  18. Clair Morrill

    March 12, 2015 at 3:50 am

    They CFL's would last longer if the transistors were properly heat sinked on a metal heat sink, also it is better to use the 13003 than the 13001
    (13001= Vceo=100, 13003=Vceo=300) the complete part number is MJE13003. Also the To-126 package will dissipate more power than the TO-92 package.

  19. Kushan

    March 12, 2015 at 1:16 pm

    Blue Ring Tester

    Many guys have asked on the schematics of the "Blue Ring Tester". you can download it from the following link. further you can get more information on this equipment and it's usage by reading Mr. Yong's previous post on the same.,d.dGc&cad=rja

  20. mustabz

    March 14, 2015 at 12:54 am

    Mr Kushan! if i could add claps in this commentary ,i will give you a thousand of them . brilliant article ,and it shows that one needs to be a little patient in handling such items,
    way to go! keep it up.

    And we continue to thanlk Mr Jestine Yong for the grerat works he does. God bless your hands

    • Kushan

      March 16, 2015 at 11:44 am

      Thanks mustabz.. you encouraging me !!! Sure, we do thanks to Mr.Yong for giving us a palace to talk !!

  21. Humberto

    March 16, 2015 at 7:46 pm

    Hi Mr. Kushan Ranatunga, good article. Congratulations.

  22. iebe

    March 19, 2015 at 12:11 am

    thanks... ^_^

    ilmu pengetahuan yg bermanfaat, saya menyukai semua pengetahuan dari sini, thanks 🙂

  23. frikkie

    March 19, 2015 at 11:25 pm

    Hi just a tip. There is a yellow powder that one can get at pharmecies I unfortunately don't know what its called in English.I do know that the athelets that do gymnastics and weight lifting put that powder on their hands for better grip.That powder you take a bit and rub it onto the copper wire,than it sucks up the solder a lot better when you desolder components.You can always strip the tv antenna coax cables.the ones that have the copper coax wires.Then you have long lengths of wire you can use to desolder components.

  24. Maurizio C.

    February 23, 2016 at 3:53 pm

    Nice article, Mr. Ranatunga. What about the initial (seconds lasting) flickering of lamps? Is still the electrolytic cap the culprit?

  25. suranga Electronics

    November 9, 2016 at 4:01 pm

    Mr- Kushan,

    i too Repaired This Type CFL Lamps

    very Good your This Article.

  26. Dilum

    March 18, 2017 at 11:53 am

    Thanks for energy saving...
    I too repaired hundreds of them.
    once I fund OSRAM 20W one got Blue colored coused by leaking DIAC
    few times I met DIAC is the problem.But most times burnt TR,Resistors & leakin CAPs.oveheating fillement is avery bad & rare case difficult to workout.

  27. wyxchari

    May 23, 2017 at 12:13 am

    Repair fused filament:

  28. Manolo

    October 25, 2020 at 4:45 am

    My experience is completely different. I do manage the lamps installed in the external part of a building, they are automatically lit at end of day and stay on all night long and automatically turned off at dawn, is that most of times the fault with my lamps is indeed in the bulb, one of the filaments get burnt and the bulb will not work anymore. I have a dozens of well functioning socket-and-circuits, because their bulbs were burnt. They last about 400-600 days (5000 to 7000 hours)


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.