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I repaired a pedal just last week that depended on the enclosure for in/out jack shield grounds, it was crackly whenever you wiggled the plugs.  A direct ground run fixed it.  I like to use a star ground to some convenient point like the input or output jack shield, with direct runs to important ground points (like charge pump grounds) and daisy chaining the others (like LED grounds.)  You can also add a ground row to the vero and tie everything there.  If you need an expander for the jack shield connector, I like this kind:

On the bench, for a quick pass/fail or to monitor while using the scope, I use one of those cute little 9V Fender Mini Twin toys.  For tweaking or QC, I use separately a solid state 100W and a tube 20W with no other pedals and a long cable.  To test flexibility I mix in some other pedals.   There are some issues that will show up under one of these conditions (especially SS vs. tube) but not the others.  If the build is for a customer, I then try to simulate their actual signal chain as closely as possible with what I have on hand.

I know nothing about amplifying harmonicas, so I'm curious.  Do you use a microphone?  If so, do you run it thru something before the amp?  Preamp, mixer, etc.  I am assuming that you'd need some conditioning and/or impedance matching for a mic-level input before you hit the instrument-level guitar amp?  Or maybe not.

AionFX has quality kits as well.

This is some great information! 

I've been using my Atlas DCA75 to test the diodes, but I noticed that it's testing at 5mA.  When I see the 0.35 Fv, should I be reading that at 1mA or 5mA?  I have a particular darlington Rangemaster I build (thanks Midwayfair for turning me onto those years ago), so I have only really used my Atlas to measure Germanium transistor leakage.  I believe the software can construct voltage curves if I can get it to run on my Mac.

Yes, the DCA75 will show you the full curve if you can get that USB link working, maybe with a Windows emulator on your Mac?

0.35V on a Ge diode would be closer to 1 mA than 5 mA.  Diode Vf is always relative to a current, and it's not much use without it.  The DCA75 (and DCA55) show you the measuring current (usually 4 to 5 mA.)  I have a Fluke VOM with a diode function, and it measures at 1 mA (I've deduced), so those results don't match the DCA.  I would guess that published Vf measurements not referencing a current would have been made with a VOM, so around 1 mA.

If you want to see a large number of Ge diode curves, including the ones discussed here, try https://www.freestompboxes.org/viewtopic.php?t=32837&;

Kinda.  Remember that a diode's forward voltage is a curve that varies with the current, so you'll get a different Vf result if you measure with different currents.  I have some D9E diodes, and they consistently measure 0.3V at 1 mA, and 0.49V at 4.5 mA.

Some Russian Ge diodes with similar curves include D9J, D9B and D9V.  The readily available silicon BAT42 Schottky diode measures 0.27V @ 1 mA, but only 0.32V @ 4.5 mA, so it's similar but not quite the same.  Maybe close enough, though, you could do an A/B sound check for any audible differences. 

(PS: Ge diodes (and transistors) change characteristics pretty radically with temperature.  So in addition to using a consistent current, you also need to measure at a consistent room temperature, and not warm them up with your hands for example.)

On the similar L5 preamp by Aion, I find it works best as just that - a preamp, last in the chain, and running directly into a power amp.  It's not really an overdrive or EQ pedal, it's the amplifier's preamp in pedal form.  Maybe running your Colour box before it would help?

Yes, this looks OK.  It's a Tillman preamp/boost, with a few values changed, and with an added bypass capacitor C3 that increases the boost. This circuit inverts the polarity and will boost up to about 20 dB as you said.  With the component values you give us, the low-end corner (-3dB point) is about 18.5 Hz, and the response is flat to beyond 100 kHz.  Using a +9V supply and a J201 FET, the output waveform is clean for a relatively small input signal (below 200 mV peak to peak) and gradually distorts as the input level approaches 500 mV P-P.  You will certainly hear the distortion by the time you input 1V P-P.  The hard clipping limits are around 3V positive and 4.8V negative, so the maximum output regardless of input will be around 7.8V P-P.

Might try the Misfit also

Iffin you do, be sure to get the correct op amp too (CA 3260), it does make a difference in this one.

Trust me, we've all been there, more than once!   

Just take the back off, and make some clear pics of the insides and post them.  We can start there.

Welcome!

Did you get the kit, or just the PCB?

Can you post some pictures?

The Nobels ODR line are some of my faves, you can hear demos on YouTube.  Very flexible, and less of a mid-hump than a TS.  Brian has an ODR-1 (Laureate) with added bass roll-off (a very useful mod) here at Madbean.   

Or for something completely different, try the Ibanez MT-10 Mostortion, with 3-band EQ (Madbean Misfit), I like it even better than the ODR-1, and it's even more flexible.

In some recent posts at Dirtbox Layouts, someone (maybe you?) said they had a similar problem, and IC3 (the charge pump) got hot.  If that's you, the 7660S could have been damaged, making it whistle.  You can check whether the whistle is coming from the charge pump by using an audio probe (go to https://aronnelson.com/diywiki/index.php?title=Debugging for instructions if you don't have one.)  If that's the source of the whistle, I would replace the 7660S (IC3) with a new one.   If that doesn't fix it, you can filter the charge pump DC output to prevent any noise from reaching the signal path, let us know if you need help with that.