Compaq Armada 7730MT

[Epagec]

Hello everyone

I have this compaq Armada 7730Mt (pentium 166. Mhz 1mmx laptop)

It's working well except pccard slot not working and fan not spining.

I have a short on what I suspect to be a 12v rail (related to the fan)

As you can see I removed the coil, it's ok no short on upper side but I have only 0,2V and the down side is shorted

When I inject I have 3amps at 1V but nothing going hot with thermal cam.

Do someone knows this board and could tell me which voltage rail it is (and what it's used for)

I don't konw if the coil could be going to the ground and what is generating this voltage rail.

Thank you so much for your help in advance.

[mon2]

Share the topside markings of Q509 that is north of this removed inductor.

[Epagec]

Markings are
S9712
BCP51

Top pin and middle pins are both 0,2v 2 pins down on both sides are 18,5V, no shorts when coil removed

[mon2]

Is there a schematic available for this unit?

We now know that Q509 is a power transistor and the removed coil mates with the collector pin.

https://assets.nexperia.com/document.../BCP51_SER.pdf

[Epagec]

I don't find any schematics for this unit, will check again but it's quite old.
I don't understand how this power transistor is supposed to work.