SMD code 2F - NPN or PNP Tranzistor?

[2X]

Hello,
I have an AC(230Vrms) to DC(17VCD) power supply. It has short(green circle) some components and burn (red circle)some others. One of the burned components was an SMD component with 2F marking on it. I designed a part of the circuit. I can't understand the yellow highlight how it works and what is the use for the Q6 and D6 (maybe for discharge the capacitance at the gate of the mosfet but the diode is in reverse), but what do you beleive that is the Q6 tranzistor... an NPN or a PNP?

2F
http://markingcodes.com/search/c/2F

BC850B - NPN
https://assets.nexperia.com/documents/data-sheet/BC850B.pdf

MMBT2907AW - PNP
https://gr.mouser.com/datasheet/2/849/mmbt2907-2577580.pdf

[magic]

Are you sure about D6 polarity, location and connections?

Assuming that your schematic is correct regarding Q6, it has to be PNP because NPN base-collector junction would limit voltage after R23 to no more than 0.7V - not enough to ever turn on the MOSFET.

edit
Blown gate drive circuitry means that significant current was flowing through it from the shorted FET. This current went to the chip (nowhere else to go), so the chip may be damaged too even if it isn't visibly smoked. I recommend some testing without power FET installed, or simply replacement, because powering up the whole PSU with bad control chip may cause similar disaster to happen again.

Make sure that there is no short in parallel with R1 - this could be one possible trigger for this kind of failure, and it would happen again if not corrected.

MMBT2907AW - NPN
https://gr.mouser.com/datasheet/2/849/mmbt2907-2577580.pdf

2907 is PNP.

[2X]

Are you sure about D6 polarity, location and connections?

Assuming that your schematic is correct regarding Q6, it has to be PNP because NPN base-collector junction would limit voltage after R23 to no more than 0.7V - not enough to ever turn on the MOSFET.

edit
Blown gate drive circuitry means that significant current was flowing through it from the shorted FET. This current went to the chip (nowhere else to go), so the chip may be damaged too even if it isn't visibly smoked. I recommend some testing without power FET installed, or simply replacement, because powering up the whole PSU with bad control chip may cause similar disaster to happen again.

Make sure that there is no short in parallel with R1 - this could be one possible trigger for this kind of failure, and it would happen again if not corrected.

MMBT2907AW - NPN
https://gr.mouser.com/datasheet/2/849/mmbt2907-2577580.pdf

2907 is PNP.

The chip I measured it with multimeter on the PCB and the pins 7 and 6 was shorted. I removed the chip from the PCB and the short removed from the PCB but was still exists on the the chip (TDC4863). I will install a new one and I will check (with a portable oscilloscope - OWON HDS2202S) if on the pin 7 give square pulses.

Are you sure about D6 polarity, location and connections?
It is very strang to me... I wll check it again with the multimeter.

Thanks for your reply.

[fmashockie]

Here's an application circuit attached for the TDA4863 for your reference.  It could help you verify you've traced out your circuit correctly.