It is a 4-wire PC PWM Fan that I broke by swapping the GND and 12v for 2-3s. I did it because I thought it could reverse the direction like in other motors. So, something is dead in the fan.

I remove every case and just leave the circuit with its inductors, and its blades. Also, I provide pics of the main chip in the circuit (using a cheap microscope).

Some friends said to me that probably the chip or the diode are broken, but studying the chip would be really hard, and without the real numbers in some components would be almost impossible to replace it.

I have more pics if it is necessary. Also, I can take more. I think the chip is K408 Y331, or something similar.

I was searching for variations of this chip and found almost nothing, just the Y836.

I would like some help to get any of these:

a) How can I repair this circuit? How can I get the broken components?

b) In case the a option is almost impossible, How can I reuse the motor + blades? I can desolder the 3 legs of the motor, and start from zero, but I have seen many different tutorials on internet that maybe are not applicable for my 12v 0.3A fan with 3 legs. I would like the easiest way (Arduinos? ESC? new custom circuit? any chip?).

Thank you

All pics (circuit, chip, motor): https://imgur.com/a/Rua0ZpN

enter image description here

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    \$\begingroup\$ Repair is pretty much pointless and even if you do it for the sake of doing it, time consuming to find the broken part, and a replacement part. Reusing the motor is possible by getting a new brushless motor control. But also pretty dumb due to cost/time/effort compared to simply replacing the fan. It's a commodity part, the cost of replacement is much much lower than repair. \$\endgroup\$ – Passerby Feb 7 '19 at 7:50
  • \$\begingroup\$ Any recommendation for reusing it? The simplest/cheapest way to solder those 3 motor pins to a new circuit (eg. arduino-based). I have seen that ESC are about 4-8€, quite expensive. Maybe you can point to me another alternative and answer this post to give you the accepted answer. \$\endgroup\$ – user3819881 Feb 7 '19 at 12:53
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    \$\begingroup\$ Chalk it up as a learning experience. You reversed power to an electronic circuit which was not meant to have reversed power. You've probably fried the chip and possibly fets/transistors. No real way of fixing it, especially with no information on it. Recycle and move on. \$\endgroup\$ – StainlessSteelRat Feb 7 '19 at 16:37

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