[SOLVED]: Buffer pedal adding distortion?

[Kipper4]

We've all been there Jordan. Glad you haveit working
I make mistakes everyday in circuits but I think I'm improving gradually.
Rich

[induction]

Don't be hard on yourself. Mistakes are how we learn, and debugging is a great way to spend quality time with your circuit, figuring out how it works.

Glad you got it sorted.

[Mark Hammer]

You wouldn't think that, with only 3 pins, there would be many ways to make a mistake, but you'd be surprised.  I can't begin to count the number of times I've had to rebuild something on perf, because I thought the transistor was supposed to face this way, when really it was supposed to face that way.

Probably a good idea to do two things, in future:

1) Always have a datasheet, or maybe even a few, handy for the transistor you're using.  It doesn't happen often, but sometimes one manufacturer will decide to make the same part number with the pins flipped around differently from another manufacturer.  Plus, some datasheets will show the same overhead (or is that underchin?) view of the transistor that bamboozled you, while another will show a proper 3D drawing that gives a much clearer idea of what pins are what.  So, having a couple datasheets from different manufacturers can help corroborate what pins are where.  And since they're free for the downloading, what the heck, snag 'em.

2) Try to use sockets for transistors.  I'm fine with breaking off three of the machined pins you can buy in rows of 20 or 40, but I understand why some folks like official transistor sockets.  Using a socket lets you make as many mistakes with pin assignment as you want, without subjecting the transistor to repeated heating up.  Also lets you try out different ones to see how they make a difference.

[Frank_NH]

An interesting aspect of this particular problem is that even though the transistor was flipped, the circuit still "worked".  This issue came up in another forum where the person said they could flip the transistor around and the circuit still "worked" (I think it was a buffer as well).  I did some research and found this explanation:

http://electronics.stackexchange.com/questions/29756/bjt-in-reverse-active-mode-of-operation

[Seljer]

It's also much less obvious to diagnose in a fuzz pedal where you're *are* expecting the sound to be all distorted

[anotherjim]

If your meter has Hfe test sockets - play around with it. See what it does if you deliberately swap C and E. Prove your transistors this way before using them. (this won't damage them)

Also, use the diode test on the meter to prove the transistor Base-Emitter and Base-Collector junctions. Also that Collector-Emitter reads open circuit. This can be done with the transistor wired in circuit in most cases (with the power off of course).

Actually, a lot of experienced builders will rarely fall into the trap because they get a bit obsessive about transistor gain and will have measured the Hfe so are certain of the pinout.

Just wait until you make something with JFETs. I can never remember which is Source and Drain - and they will work even better than a BJT with these swapped.

[PRR]

> You wouldn't think that, with only 3 pins, there would be many ways to make a mistake

I've made mistake with only 2 wires.

Many times. (More than twice.)

> even though the transistor was flipped, the circuit still "worked".

That's what I would have expected.

The emitter junction breaks-down at 7V but in many 9V circuits there's 4.5V, so the emitter will stand the stress near as good as the collector.

As that link says, the current gain is better if used as intended, but the reverse-connection gain is often significant, enough to "work" better than a jumper cable.

Most JFETs have negligible difference between Source and Drain for audio purposes. There may be a few pFd less capacitance the "right" way, which matters for radio, not for audio.