Peabody wrote:
While the pop-up flash on my Canon XT camera works fine, the hot
shoe doesn't work.

2SK2715, a 500V N-channel MOSFET. That would make perfect sense in
this application.

But the problem is that the transistor is soldered onto that amber
flexible plastic stuff that passes for a PC board these days. I've
never attempted to desolder or resolder anything to that stuff. I
have a 30-watt iron. Can anyone give me advice on that?

An alternative would be to wire in the replacement in in parallel
with the existing part, probably just soldering to the old part
leads and trying to stay away from the plastic PC board as much as
possible. If I have room to do it that way.

And finally, this transistor appears to be pretty obscure, and
while Mouser carries it, it would be nice if I could use something
I'm more likely to find locally - an NTE part perhaps. It wouldn't
really have to have a 500V DS rating. As a practical matter, I
think 50V would be plenty - modern flashes don't go over 12V. So if
anybody knows of a common N-channel MOSFET that might work, please
let me know. But it has to be small.

Any luck finding a substitute in a power supply, such as one for a
PC? 500V MOSFETs are common in them.

I think you have to use a 500V transistor for the 12V flash for the
same reason vehicle ignition systems use transistors rated for
hundreds of volts on the 12V side of the ignition coil -- big voltage
spikes.

You could practice soldering the flexible circuit boards of junked PC
keyboards. I think they're made of mylar polyester, while that brown
flexible plastic in your camera is probably kapton, a plastic with a
much higher melting point.