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I finally got my first PCB through in the post today. Very happy with it, but I made a very amateur mistake in my excitement and eagerness to have it ordered. I seem to have used a 2N2222 part with the wrong pin out.

enter image description here

R5 should be to the base of T1, however all the 2N2222s I have seem to have the base on pin 2, not pin 3 as shown here.

Does anyone know how I could track down a version of this transistor that has the pin out of 1 - emitter, 2 - collector, 3 - base? The datasheets I've trawled through so far seem to indicate I might be out of luck.

Lesson I've learnt here, don't autoroute without checking very carefully.

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  • \$\begingroup\$ Baptism by bodge :D \$\endgroup\$ – Wesley Lee Feb 22 at 12:24
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Just about any Japanese-pinout TO-92 part 2SCxxx will be pinout compatible. Most BCxxx parts are C-B-E, mirror of the US-style PN2222A.

I'll not attempt to match the characteristics since most TO-92 BJTs these days are not used anywhere near their ratings and your layout suggests it's only conducting a modest current. If that's correct, you could look at the 2SC1815 and see if it meets the circuit requirements.

Don't make this mistake with surface mount parts- they've mostly been standardized and you won't have such choices available. Also, be sure to double-check hole diameters before "signing off" on a through-hole footprint. It's quite irritating to have the holes a bit too small.

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The BC637/BC639 has the correct pinout and can handle about the same voltage/current. You might have to modify the base resistance a bit because of gain differences.

Assuming this is only for simple switching purposes.

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Insulate leads 2 and 3 (strip the insulation from a piece of insulated wire) and cross the connections over. OK for a prototype.

Or, cut the tracks leading to pins 2 and 3, and cross the connections over with a couple of short pieces of wire.

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BC637/639 proposed by Unimportant are obsolete , try BC63916, you can buy from Farnell-Newark , same pinout with similar parameters.

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