Help de-bugging Whisker Biscuit

[PB Wilson]

So my former student and I finished soldering up a Whisker Biscuit and when the moment of truth came and we stomped the switch.....nothing.  
I checked the wiring, the circuit, the soldering (I even went over each solder joint to re-melt any possible cold solder joints, but got nothing once again.

I re-read the various info online on what to do if your effect doesn't work and may solder up an audio probe soon. I did get some voltage readings from the transistors and have an idea that it's the MPSA13. Here are the readings I got going from left to right on the schematic:
2N5088
C 4.38
B 0.66
E 0.04

MPSA13
C 8.34
B 0.0
E 0.0

2N5088
C 4.30
B 0.66
E 0.04

Any help or ideas? By the way, I did look up the pinout of the MPSA13, but could Steve at Smallbear have some wacky pinout Darlingtons?

[brett]

Hi.  The base of the MPSA13 has to be 1.4V above the emitter for it to work (ie E=0V, B=1.4V).  Check that the 1N914 is in the right way around and that the 10k resistor on the collector is soldered in OK.

good luck

[PB Wilson]

Update: I fished out the Whisker Biscuit from the "to do" pile of projects and gave it the once over with my DMM. After a minute of desoldering I swapped out the diode and using a couple alligator clip heat sinks, got a new one in place. Checked the pinouts of the transistors (Thanks GGG for posting that table!!!) and fired it up.

SUCCESS! What a fun pedal. Quite a range of tones available with a turn of the tone knob. My former student will love this pedal. He'll be the talk of the middle school music room! I almost don't want to give it away. Good thing I've got a bunch of extra parts in my stash.

[jmusser]

Congratulations! I'm glad you were able to get the problem ironed out. I don't know gobs about biasing, but I knew you had problems with 0 voltages on that one transistor. I have been very impressed with the sound sample of this pedal, and ultimately will build it. There's too much ahead of it right now that I have bagged up to work on. I'm trying to get my 15 year old son into building pedals. I figure I'll start him off on the Easy Drive. That's neat for you to have built this project with a student.

[PB Wilson]

It really was fun working with a younger person. I really get a lot out of teaching and sharing a hobby of mine with a former student was really rewarding. The way we went about it was I showed him the layout, put the parts in place and he soldered them in. It took a little while to get it down correctly, but I hope he is more empowered to try new things once he sees that they aren't as difficult as they may seem. Anyway everything worked out in the end and most of all, it keeps him from buying crappy pedals at Guitar Center! :wink:

[Danny G]

I just built a Whisker Biscuit.  Nice build, mean little pedal!  Think I'll put it in a box.