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Oh, my Friday is so much better now.... Glad to help out with my donation, not really enough considering the support given.  Wishing the best for Function (fx)!

Kudos gentlemen!

~Mike

The Sparkplug is up and working, sounds good too.

When I wrote, "... missing something "Stupid"", I was right.  After thinking about an ungrounded cap, having checked them multiple times and resorting to lead dressing what did I discover, that the polarity of the I/O leads were reversed. UGH, duh, but reminds me of day three of circuit analysis and the prof's story of solving a nonfunctioning transmitter with the insertion of the power cord.  Yeah!  Just a reminder to look at the simple things first!

Cheers,
~Mike

It is unboxed, always test before boxing.  All is grounded too, and am beginning to think it's wiring and/or hardware.  It's gotten a bit kluged up with my removing and reinstalling the transistors.  On my last adventure I noticed that the LEDs light when checking pin 3, light upon oscillation (makes sense), but am getting a "theramin" effect off the output jack, including LED illumination. Weird! With the voltages looking good, caps, resistors, and pots checked I am going to try replacing the pots and using a cleaner lead dress--not bad but am taking the next step.

Thanks for working through this with me, Jacob.
~Mike

Oops, I do have 0v on pin 4, guess that mis-entered that one. 

I'm kind of at the end of my ability to debug the old version of the Sparkplug, having build and debugged many circuits I seem to be missing something "stupid".  There's a horrible "open ground" type noise when adjusting the volume, which turns into an oscillation when adjusting the cut.  At maximum volume and gain there is some output and the "open ground" noise and oscillation are minimized but the output is barely there.  I've checked the pots, caps and diodes, and have tried replacement ICs, have reflowed and inspected for solder bridges.  Any suggestions/ideas on what I'm missing?  Note: I wired the pots instead of using PC pin type. 

Voltages on IC

1  4.20       8  8.45
2  4.20       7  4.20
3  3.76       6  4.20
4  4.20       5  3.76

Input voltage: 9.20
Voltage post input diode: 8.45 (Vbb)
Voltage at (Vcc) is 4.20

Thanks for any ideas!

Cheers,
Mike

I'll try to work some demo stuff out.  Between perfunctory guitar skills and using an iPhone to record there will be a lot left to the imagination. 

I might add a couple of notes on the sound of the mod while I figure out some demo stuff. (This might take some time) What I find cool is that it is possible to get the sound of an overheated output transformer, just adding to the Jimmy Page, Keith Richards type sound. Equally, instead of only getting huge sustain from the standard circuit I've found that dialing down the fuzz and turning up the volume it's possible to get a really "clipped" sound. It can get pretty messy and takes a little getting used to playing, and discovering "happy accidents".  It sounds best, to me, playing DADGAD and open G tunings.

~Mike

Just thought I'd share a slight design change to the Pasty Face. After building the Pasty Face, and finding the gain slightly above unity (built using some Chinese BC109 NPNs (super low hfe 110--matched as required by the circuit design)) the sound, best described as "all fuzzy", I thought through the circuit a little and came up with an interesting mod by inserting a partial bypass between the base of Q2 and Q1 at the Fuzz pot #1 and Vol pot #3 (there is a SPST switch placed at the junction to switch allowing function change: Fuzz/Boost-fuzz).  Additionally, I removed the Tone pot and inserted two 22K fixed resistors bridging 3 to 2, and 1 to 2. Other "mods" were including the 1M R1, jumpering R11 and removing D1 and R12.  The remained of the circuit is based on the Sola circuit.

The goal was to utilize Q3 as a largely "clean" boost, keeping some signal passing through Q2 for a fuzz signal, bypass and "blending" determined by the Fuzz pot and Volume pot.

The result?  Mostly what I expected, but more.  Because there is some inherit lag in the signal passing through Q2 there is a "fuzz bloom", kind of a slight harmonizing behind the "clean boost".  The sound, a bit more like Jimmy's sound on Kashmir.  Of course there is a little switching noise, but my thinking is that I'm going to use one or the other settings and not toggle between the two functions.  I figure that a small value cap between the contacts will likely eliminate the pop.

Anyone try something similar?  Results?  Other mod ideas? Results using other NPN, or higher hfe transistors?  I'm really liking the sound through a single ended EL84 amp. Using the circuit with a PP there's a loss of the fuzzy "harmonizing".

Cheers,
~Mike