How to identify transformer pin out in genuine mobile charger?
It is a &quot;high-frequency oscillator&quot; of sorts. This is a SMPS or switch-mode power supply. Likely on the underside you'll find at least one integrated circuit and possible switching transistor (some IC's have the switch built-in.)
High-frequency transformers like this green one are very often custom-made for mass-production. You can try searching for the number printed on it, but might not find anything. Even prototype units, made from a transformer kit, are all custom-wound. Could disassemble it...
Without destroying it, you could desolder it, and use a multimeter on resistance scale to map-out what pins have what resistance to what. Pins with resistance are a winding. There are usually one primary winding (sometimes center-tapped), at least one secondary winding (also possibly center-tapped), and likely a single &quot;aux&quot; winding. Very often, several pins are not used and have no wire even going to them.
Identifying which winding is which can be challenging. If designed to boost voltage, the primary winding will likely have a lower resistance. Conversely, a &quot;buck&quot; design to reduce voltage will likely have a higher resistance on the primary. The aux winding doesn't have to power much, so may have a higher resistance and lower inductance.
Then use an LC meter to measure those resistances to get their inductance. Sketch these values onto paper in the shape of a proposed transformer schematic. Someone here could likely verify if it seems right.
Then get a signal generator. Set it to AC output, perhaps 1 volt. Connect it to the proposed primary. Measure the voltage at the primary, should be 1v. Then measure the proposed secondary and other windings. See if it agrees with speculation. A little trial-and-error like this and the transformer can be &quot;mapped.&quot; Then go shopping for a similar one with these specs from any of the big electronics component vendors.
Note, CapXon brand electrolytic capacitor are notorious for failing prematurely.