SOT23 help for identify unknown device.

[rauldm]

Hi, I'm repairing a commuted power supply for charging 48 V Pb/acid batteries. it works with 2845B PWM current controller, for main power converter and works also with 2843B PWM current controller for circuit for boost converter. The problem is the 2843B it has connected  output to little device in SOT23 format but I cant indentify, I think is a BJT switching transistor but, 2843B is controller for MOSTFET.
I atacched  a pic.

Regards.

[Yansi]

Likely a 2SA2065. Check your circuit if it fits the purpose and circuit.

http://pdf.datasheetcatalog.com/datasheet/toshiba/3087.pdf

[rauldm]

Thanks, I think is near to application and circuit type, is a boost converter.

[rauldm]

How you found the device?

[Yansi]

Just by googling "SOT23 marking WK".

Not sure about the "4" suffix though, but I could not find any single device with marking of "WK4". 

You need to understand your circuit first to be able to assess if the part number you have come up with matches the desired circuit it is used in.