Flyback transformer testing and replacement

Thread Starter


Joined Dec 22, 2018
Can anyone help me diagnose this transformer or suggest a replacement?

Primary coil takes 5v and the feedback coil takes another 5v. I cannot get any output voltage so I assume it is faulty.

But it outputs to a 3v power regulator and a 1.5v power regulator so I suspect at the same 5v range.

As you can see by the photos. I get no output no matter what.

It has printed on it 3305 n181 and part number is S1673305 and unfortunately I cannot source a datasheet or the part.

IMG_2713.jpeg IMG_6771.jpeg


Joined Sep 30, 2009
You're probably not getting an out put because your putting DC on the primary. Transformers don't work with DC. Or at least not unpulsed DC. What do you get if you just touch and release the DC to the primary? Unless there is an oscillator built into that coil the DC to the primary was being pulsed somewhere else in the circuit.