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

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

Picture of 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 :

Step 2: How to find the pins location of the primary coil?

Picture of How to find the pins location of the primary coil?
With a simple ohmeter this is very simple, you will find easily the primary inputs because the coil resistance is about 1 ohm 
Bumba Lodh3 years ago
i don't have 24 volts dc power supply but i've 12 volts dc power supply
please give me a advice
Jimmy Proton (author)  Bumba Lodh3 years ago
That might work, if it does then you should see around 3 volts on your meter.

I can confirm that reading.

What multimeter is that it seems that everybody has that multimeter

If you can read it is NG60... :)

trekman4 years ago
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.
Jimmy Proton (author)  trekman4 years ago
flybacks often have more than one primary, use whichever one you like.
what if you use multiple primaries?
i could not find the primary and secondary pins/.........
a2262632 years ago
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?
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
Alrighty. Will do. Thanks!
your welcome
will a 9 volt battery work for finding the primary and secondary coils ?
R.A.T.M3 years ago
so i know what the main THT out put is but i have 3 other wires hanging about what are they 4
geckomage3 years ago
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.
Rbwood3 years ago
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 (author)  Rbwood3 years ago
Your welcome but i do not take full credit for these.
ARJOON4 years ago
don't forget guys. ac from wall socket will not work. frequency is too low.