I got a couple of SMC network switches (EZ Switch, SMCGS5, HW rev. A1), of which one is broken on account of something applying 12VDC to the 5VDC input. Looking at the broken switch's PCB, I can see that one component in the voltage input section is fully charred and basically vaporised. Comparing with an intact PCB I can glance the following data:
- Silkscreen name: Q3
- Package type: SOT-23
- Markings (on intact version): N59M.
- Further PCB markings: D (near the top), G, S (two pins on the lower end).
I have done extensive searching to find anything resembling a match, but other than that it is a JFET/MOSFET transistor I have only drawn a blank.
Anyone have a clue what transistor this may be, and what to replace it with?
U2 is marked FP5453 and seems to be a Dual PWM Controller for DC/DC circuits.
Here is a picture of the board (click to zoom):