Power Protection in a Dunlop MC-404 Wah....What is/was this transistor?

[drummer4gc]

Hey everyone,

I'm working on a MC-404 wah that has lost its magic mojo smoke due to plugging in an incorrect power adapter.

From the power jack, 9v+ enters the circuit first through Q3, an SMD transistor, which is the part that burned up. It came out in pieces, so I couldn't read the code to figure out what to replace it with.

Here's an image of the pads where it once existed along with my temporary fix of jumpering 9v+ straight into the rest of the circuit:



The top pad connects to 9v+ at the jack. The middle pad sends 9v+ to the circuit. The bottom pad connects to the anode end of the 1n4148 diode, which is in series with the 33k resistor to ground. I'll draw something up if it's more helpful to see it, but I figured that was simple enough to imagine from the picture.

I know this has to be one of the many power protection schemes out there, but SMD always throws me a bit. Any idea what Q3 may have once been before it kicked the bucket?

Thanks!

[PRR]

WHAT was plugged-in which killed this circuit?

[drummer4gc]

Not 100% sure...I assume it would protect against reverse polarity at a reasonable voltage, so maybe it was an adapter with AC output that did it in.

A run of the mill PNP did the job though, thanks for the help!