Two pin fluorescent bulb with CFL circuit

Ever since Thomas Edison invented The Incandescent light bulb , The technology behind artificial lights have changed a lot .People started to try different energy efficient approaches towards artificial lightning, As a result in year 1901 Edmund Germer invented mercury vapor lamp ,which is the blueprint for the modern day fluorescent lamp .In the age of LED bulbs people still uses fluorescent lamps in day today basis . Specially in apparel industry  , They use  two T8 or T12 fluorescent tubes to reach the illumination levels that required for their operations. Although fluorescent tube lamps are being replaced by CFL (compact fluorescent lamps) and LED bulbs,There still fluorescent tube lamps available in many households  .

Electronic and Magnetic Ballast

Fluorescent tubes require two other components in order to operate. These components are the ballast and the starter .Magnetic ballast and Electronic ballast are the two types of ballasts are being used with Fluorescent tubes. Magnetic ballasts are old school and being replaced by electronic ballasts due to it’s energy efficiency and compact design .Most importantly CFL bulbs doesn’t require any additional components for it’s operation .

Like the other bulbs ,CFL bulbs have a lifetime. At the end of that lifetime the bulb will blow out. The element of the CFL that most likely to be go bad is the fluorescent tube, leaving a good electronic ballast inside .Since CFL is basically a compactly designed fluorescent tube with a electronic ballast, We can use it’s circuit (The electronic ballast) to light up traditional fluorescent tube bulbs . In this tutorial lets look specifically into how to use the electronic ballast circuit inside the CFL bulb to light up the two pin fluorescent tubes .

Two Pin Fluorescent Bulb

Two pin fluorescent lamps comes under the F9BX/827,F9BX/840,F9BX/841,F9BX/830,F9BX/835,F9BX/865,F9BX/SPX27 and F9BX/SPX41 model numbers .These two pin fluorescent lamps require G23 Holder or the fixture.  You might have mistaken two pin fluorescent bulb with CFL ,Because it has only two pins to connect to the holder or the fixture . Fluorescent tube should have at least four pins right ?. How come these have only two pins ? .

Two Pin Fluorescent cross section

Two Pin Fluorescent Inside

The answer is inside the fluorescent bulb itself. These two pin fluorescent bulbs have starter built into it .So where it is ? ,If you look closely you can see a cuboid  structure between the two pins ,The starter is placed inside it .That is where our other two pins at .These two pins are connected with the starter that is inside . Since the starter is inside the bulb , All you have to do is connect the ballast in series with the fluorescent bulb.

2pin fluorescent Wiring Diagram

Wiring Diagram

Here is the wiring diagram of the of the two pin fluorescent lamp .In this diagram you can see the ballast is in series with the two pin fluorescent lamp . The voltage and the wattage of the ballast must match with the voltage and wattage of the fluorescent lamp . Since the starter is inbuilt , External starter is not required .

Two Pin Fluorescent Bulb With CFL Circuit

The first step is to choose a CFL circuit (Electronic ballast) that matches  the fluorescent tube of the two pin bulb however if the selected circuit gives low illumination results , choose a higher wattage CFL circuit  .We recommend finding a CFL circuit that matches  the  wattage of the two pin fluorescent tube bulb. If the wattage of your circuit is lower you may get low illumination from the fluorescent tube . If you select a higher wattage circuit you may get a good illumination but it may limit the lifetime of the tube .In order to connect the fluorescent tube with the CFL circuit we need to access to these hidden pins and we have to remove the starter .

1st Method

2nd Method

B22 Holder Modify

1st Method – Easiest way is to cut the bottom potion of the cuboid structure ~7mm above the bottom of the casing using a hot cutter or mini hand saw .Be careful not to cut the starter components inside the casing.Once you are done remove the starter by cutting the pins and solder two wires to the fluorescent tube leads that previously connected to the starter .


2nd Method –  In this method we can remove the bottom casing of the bulb without cutting it .You have to use a small drill bit between 0.5mm and 0.9mm and drill the two pins from the bottom to remove the copper clamp that holding the single wire inside the pins, which comes from the fluorescent tube. Drill it pass the part that clamps the wires .Then remove the bottom part of the bulb ( depend on the bulb design you may need to use a pry tool to unclip the bottom part.Cut the leads of the starter components.


Now we have the access to all 4 pins , solder 4 wires to these leads. Use heat shrinking tubes to protect the leads from shorting  .Drill a hole in the bottom of the bulb casing and the bottom of the B22 holder .Run the wires through it . Solder these wires to the CFL circuit .

Two Pin Fluorescent CFL Wiring diagram

Before powering up – Put the CFL circuit inside a casing and secure it . Connect the AC source to the CFL circuit . Don’t touch any open wires or the circuit parts while it is connected to the power source .  Turn on the switch !


Not lighting up ? , Let’s Troubleshoot .

Checking the Fluorescent Tube

Checking the Fluorescent Tube

 Checking the CFL Circuit

Checking the CFL Circuit

Checking the filaments of the fluorescent tube – Put the multimeter on Ohm (Resistance) mode .If you are using a manual multimeter put the selector on the lowest Ohm scale range .  Touch the two leads in each side of the fluorescent tube with your multimeter probes (As shown in the image)  .The resistance should be  less than 10 Ohm. Check both sides . If any side have  resistance over 10 Ohm , You most likely to have a bad fluorescent tube filaments  . Even the filaments are good ,There is still a chance that evaporated  coating on the electrodes will cause the tube to go bad .Check the ends of the tube , If you spot dark or black rings around the tube,The tube is most likely gone bad .Replace it .

Checking the CFL Circuit[Proceed with caution involves high voltage]. Due to the high voltages that generated at the initial phase ,We don’t recommend checking  the output voltages of CFL circuit using a conventional multimeter .You need a True RMS Voltmeter with at least voltage Range of 1000 Volts AC .

1 comment

  • Harsha 1 month ago



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