How to find the primary and the secondary coils of a FlyBack transformer

The main problem, in most cases, is that you don't know the pinout diagram of a flyback transformer. So, I shall try to give you a simple method to find the primary coil input pins and also the 0 V output pin of the HV secondary coil.

-=I do not take full credit for this=-

Step 1: How to find the 0 V pin connection of the secundary coil?

With a common digital ohmeter it is impossible to find the secondary coil pinout because its resistance is much too high. The main HV output is simple to find : this is the big red cable with the suction cup, but you need to find the 0 V pin of the secondary coil on the flyback transformer. So, I give you a simple method to find this 0v pin :

a) You need a 24 V DC power supply and a digital voltmeter set in 20 V range. Connect the + input of your voltmeter to the THT ouput plug ( in the suction cup ) and the (-) to the 0V of your power supply. Then, with the +24V output from your power supply, test each pin of your flyback transformer. When you measure a voltage between 5 and 10 V you have found the 0 V pin of your secondary coil. This is very simple... Look at the diagram and the photo below :

Comments

[abhilash476]

i could not find the primary and secondary pins/.........

[crazy-blender]

What multimeter is that it seems that everybody has that multimeter

[a226263]

I'm trying to find the pins to the primary coil. I bought a new flyback a couple of weeks ago. My flyback has 10 pins. I got these results:

Pins ..... Resistance
1 + 5 .... 2 ohms
1 + 9 .... 1.8 ohms
5 + 9 .... 0.9 ohms

2 + 8 .... 0.9 ohms

3 + 4 .... 0.8 ohms
3 + 6 .... 0.8 ohms
4 + 6 .... 0.6 ohms
All the other combinations (i.e; pins 1 + 3) produced no resistance, so that means that pins 1 + 3 are not connected. Conversely, this means that pins 1+5+9 are connected; pins 2+8 are connected; pins 3+4+6 are connected; and pin 7 and pin 10 are not connected to any other pins.

The first problem is that many of these gave me a resistance close to 1 ohm, so I still don't know which pins to use for the primary coil.
The second problem is that a flyback should have two sets of connected pins; pins that connect to the primary coil, and pins the connect to the secondary coil. However, I seem to have 3 sets of connected pins (or five sets, depending on how you count). Does this mean something is disconnected inside my flyback?

I didn't know what to do, so I just went ahead and connected it to the CFL circuit. I tried pins 5+9, 2+8, and 3+4 as the pins to the primary coil, along with every combination of the 4 pins on the CFL circuit, but did not get a single arc for any of them. Does this mean that my brand-new flyback is bad?

[crazy-blender]

it might be bad double check with each set of pins and if it still does not work buy another flyback and see if it works

[a226263]

Alrighty. Will do. Thanks!

[crazy-blender]

your welcome

[crazy-blender]

will a 9 volt battery work for finding the primary and secondary coils ?

[R.A.T.M]

so i know what the main THT out put is but i have 3 other wires hanging about what are they 4

[geckomage]

hey man, ive been searching and searching on how to find these and everyone always gave some far out crazy ways that i could not get to work. but yours has. so i would like to thank you! :) with a continuity meter i found that there were 2 pins with no matches (one turned out to be hv ground) then 3 pins with matches. 2 of those made the 1 ohm resistance thing for the primary coil. and then 7 pins all seemingly connected together with about a half ohm of resistance between them all. if you could explain what that is it'd be appreciated. also i couldnt get my slow volt meter to read a spike of 30ish v. but i did get it to read about 13-15 with a 9 volt battery pulsing it. and the other polarity got like .3v or somethin. so i'd say i found a winner ;) ima make a driver now and hope i dont blow up my transistors. haha. thanks so much! :) i wish you the best of luck in all your endeavors.

[Bumba Lodh]

i don't have 24 volts dc power supply but i've 12 volts dc power supply
please give me a advice

[Jimmy Proton]

That might work, if it does then you should see around 3 volts on your meter.

[Rbwood]

I have to say thank you so much! Your instructions are the one and only set of directions that actually worked for me. Thank You.

[Jimmy Proton]

Your welcome but i do not take full credit for these.

[ARJOON]

don't forget guys. ac from wall socket will not work. frequency is too low.

[trekman]

The fly back transformer I have came from a 19” TV. I followed the instructions and found the 0 V pin and tested for the 2 primary pins. I got very low reading using a 9 volt battery. I happened to have a 9 volt A/C adaptor but the output was 9 volt A/C so I used that to find the primary coil pins. The thing is I found 2 sets of 2 pins that give me 35.5 and 34.7 volts output. Pines 9 and 10 also pins 10 and 1 give almost the same output. Which 2 should I use? This reading is on the A/C scale on my VOM. Using a 9 volt battery I was only able to get 3 to 4 volt reading.

Thanks for any help.
Tom

[Jimmy Proton]

flybacks often have more than one primary, use whichever one you like.