Step 4: Troubleshooting

Picture of Troubleshooting
The first time I build the circuit, it worked immediately. I used a 26 watt CFL.

Then I decided to get a bigger CFL and I build it exactly like the first circuit. It didn't work. I was disappointed. I thought that the CFL electronics were shot.

But when I reconnected the fluorescent tube to the four wires, the CFL worked again. I realized that this type of CFL circuit needed to "sense" the filaments in order to operate. Remember, I was only using the outer wires and leaving the two inner wires alone.

So I put a resistor across the outer wire and the inner wire. The circuit worked! But within seconds the resistor was in flames.

So I decided to use a capacitor in place of resistor. The capacitor allows AC currents but blocks DC while a resistor allow both AC and DC currents to flow through it. Also a capacitor does not heat up because it provides a low resistance path for AC currents.

The capacitor worked great! The arcs produced were very big and thick.

So in summary there two things that can go wrong:

1. You wired it wrong, either on the CFL side or the flyback side.
2. The CFL electronics needs to sense the filament and you can use a capacitor as a substitute.

Use a high voltage rated capacitor. Mine was 400V and I got it from another CFL circuit.

While troubleshooting, be very careful, you are dealing with very high voltages and high currents.

When soldering, disconnect the circuit from the power outlet.
Remove these adsRemove these ads by Signing Up
grim32712 years ago
So i got a 26 cfl and cracked in and got the circuit

4 pins 2 on each side i have

J5-6 on a pair
J3-4 on the other pair.

I have NO idea what to do now. Any help please?
nenrikii4 years ago
Im confused... mine doesnt have the four in a row mine has two on each side.... so i dont know which one to solder to U_U i dont get it.... some one please help me here
Biotele (author)  nenrikii3 years ago
The outermost pin of the pairs should be soldered to the FBT. So lets say you have pin A1 and A2 on one side and pins B2 B1 on the other side (I am imagining the pins are arranged clockwise as A1-A2-space-B2-B1) the FBT should be soldered to A1 and B1. If that doesn't make sense please post me a picture.
I'm working through this myself and I can offer some advice. My CFL boards all have the pins on opposite sides. I tried using a multimeter to measure the out put between pairs. I got nothing. By accident I was connecting my jumper leads to the 4 output pins and noticed a small spark between two pins . although this may damage the circuit It might be one method of finding the output pins of the cfl board.... (look for the pair that sparks) Once I connected this to the original pair of primary leads of my flyback transformer I still got very little arcs out of it (with a 23 watt CFL driver)
I had built a layden jar with foil tape the same night which didn't work as I thought so I attached the flyback to it and the results improved by double. It still won't be enough to power a jacobs ladder but I think I'm on the right track. I hope this helps. BTW look at the circuit board that the flyback was attached to for hints as to what pin is what. I at the very least found a pin labled B+ and a few labeled "G" which helped me choose the primary ground pins....
Maxwell Yun3 years ago
Do you know a value range and type for the capacitor that will trick the CFL board into believing that the tube is connected? I have a lot of ceramic capacitors still on an old CFL board, and I have a 10 uF and a 20 uF polarized capacitor.
Biotele (author)  Maxwell Yun3 years ago
It really depends on the circuit. I say start with 20uf then keep adding in parallel. It should work at 100uf. Also be careful of the polarization. The circuit has a DC positive and ground. Make sure you have the capacitor in the right direction or it will pop.
jj.inc3 years ago
I have two groups of two pins and each are oposite eachother from the board. Any ideas. They are labeled A1 & A2 and A3 & A4. the first group has a box with a squiggly through it and it has ptc. The other one has more spaced out pins, and i am not sure if it is acosiated, but 94v - 0
Does the polarity of the capacitor matter?
I can get green caps (well brown caps) but i dont know if i can get hv polarised capacitors.
waselsded4 years ago
in the bord of floursent 4 ends 2 and 2 any ends i used it to concted to fly back in the picture not clear can someone help me
nenrikii4 years ago
its a 32 Watt BTW
JTreehorn4 years ago
So... I've completed this project (or so I think) and I can only get a arc at a very short distance. 2 or 3 mm if I had to guess and it's very small. Sounds very mosquito-ish if that makes any sense. I'm using a 26 watt CFL and a fly back from a 20" color TV. I did somehow manage to blow the fuse in my volt meter while testing pins with a 9 volt battery so I was forced to make a educated guess as to the positive and negative of the primary coil. Will reversing them damage anything? Does anyone think that having them backward would produce such a little arc or would it even work at all? Any ideas would be greatly appreciated.
Okay, so I couldn't wait for a response and went ahead and reversed them....Same thing. Very, very weak arc. After looking closer, a 1mm gap might be over exaggerating. Any ideas?
Biotele (author)  JTreehorn4 years ago
Try a capacitor bypass.
Already did. Got nothing at all without them. Thanks but not the problem.
This is the schematic for my flyback. Could someone with more knowledge than me please identify the following... 1- Primary Coil 2- Secondary Coil 3- Primary Positive 4- Primary Ground 5- High Voltage Ground I hope you guys don't think I'm stupid for having the schematic and still not being able to tell (gotta learn somewhere). I know what I think they are, I would just like another opinion to confirm my wiring. Thanks.
jknutson4 years ago
That capacitor trick got my circuit going, but I had to put one across both sets of contacts. I used 160V caps and they seem to have survived so far. Definitely a fun project, thanks Biotele.
tsitema4 years ago
I used a 25 watt CFL, and putting capacitors instead of the filaments didn't work. Instead, I connected a 1nf capacitor and a 1 ohm bulb to the flyback in series. It worked but, after about ten second the cfl circuit exploded blowing the fuses of the room.
Biotele (author)  tsitema4 years ago
the circuit's transistors shorted because they are under rated. Get a more powerful CFL like >40W.
bronz5 years ago
In the diagram there are 4 pins.Which go in pair ,can we know which ones are +ve and which ones -ve.And also

What is the output ? in AC or DC
emcelhannon5 years ago

My flyback has 11 pins.  The 11th is the ground.  1 and 2 are the primaries.  Hooked it up and I get orange/white spark between 10 and 11.  I get purple plasma between 7 and 8.  Nothing from the HV. 
Fear- My flyback is shot.
Hope- I can stick a cap or resistor to the pins to rechannel the voltage.
What should I try?

Biotele (author)  emcelhannon5 years ago
It sounds like you transformer is shot. You need to get a new one.
arenavles5 years ago
Hi I have been trying over and over to get this thing going and I cant seem to just do it. I first tried with lower wattage bulbs and thought that was the problem, so tonight I bought a 150 watt cfl. The four wires are in pairs of two on each side. They are labeled 1,2,3,4 thats it. I tried with 2 and 4 but nothing happens. Any help would be appreciated.
I simply love this instructable. I got this to work with the 26 watt bulb. I wanted a bigger arc so i got a 68 watt one. I looked at the board and it had four pins in groups of two. I put it together and nothing happened. So i put the filament on and it worked for about 500 milliseconds.

I believe that is because the light takes to much power, am i right?

I read on that you said you can take a capacitor and put it on it, but i dont have the 400v ones. I only have a 200v 22uF and a 200v 16uF. Would those work?

Also how would i go about installing the capacitors? Like what pins do i use and polarity?

I have added pictures.
Biotele (author)  MatthewEnderle5 years ago
You can figure out the polarity by placing a DC voltmeter between the wires. Use alligator clip then turn on the circuit, don't stick the voltmeter into the circuit with your hands.
Biotele (author)  MatthewEnderle5 years ago
Ok you can try 200V cap, it might work. Any value will do. If you have a burned out cfl there are plenty of caps in them. The high voltage caps look like Chiclets gum.  You need to place the cap between one of the pairs the of wire. Each pair is a High voltage wire and filament current return wire. You have to put the cap between the HV wire and the current return wire in order allow a little current to go through the filament circuit. This little current will allow the CFL to oscillate.
Delaney5 years ago
I tried it with a 13W CFL it was a little tricky to engage. The pin layout was the "four in a row" type where the ones farthest apart are high voltage. the messed up thing about this one was the fact it had duel filament detection. I needed 2 ceramic caps.
I had to bridge 3 pins temporarily to get it to stay on. It turns out my flybacks Highvoltage coil was shot. but I got mild 0.5cm arc across the shattered PVC board that the flyback is connected to, and once I got a 1 inch arc from the CFL board. I ended up blowing a 10 ohm 1/2 watt resister I replaced it with a 1 watt resister plugged it in then FLASH... something else blew instantly. Now I'm going to try a 23W CFL. I'm just trying for a constant 1 inch arc.
ok. i got it working, but the spark will only "join" the two posts together if the distance they are apart is the length of these dashes --- yep only 3 dashes long, the CFL i used is this one:
and i used a flyback transformer from a 15inch CRT conputer monitor, also my spark doesnt move up the copper wire i used as "posts" it just sits in the same spot......
setinight6 years ago
The CFL I opened up has the two sets of wires opposite each other instead of 4 in a row. Any idea which would be the 'outer' wires in this case?
i have the same one. the pins are labeled a1-a4 anyone know which ones to use?