Debugging Fade In/Fade Out Problem

[Zounds!]

I built a Black Arts Toneworks Quantum Mystic from the layout here: http://tagboardeffects.blogspot.ca/2014/05/black-arts-toneworks-quantum-mystic.html
Powered with a bunch of other pedals off a 1Spot, but I'm nowhere close to the 1Spot's max current. The pedal's volume was too low when I built it, so I added a Stratoblaster between the board output and the bypass switch.

The problem: Often when I turn the power on my pedal board on the pedal will be silent. After strumming for a few seconds the sound will creep up until it's at full volume. This isn't such a big deal, but when I'm playing clean, I'll kick the pedal on, here the big distorted effect, and then have the sound it quickly fade to silence for a few seconds before fading back in. Once it's faded in again it acts totally fine until I repeat the stomp off/stomp on cycle....but only sporadically. It's pretty unpredictable so it has been difficult to troubleshoot. I added an extra 3pdt to the layout set for one side to bypass the gain pot for full gain and the other side to use the gain pot as normal for lower gain settings. To make matters weirder, I could swear this fade out thing only happens when I'm on the "full gain" setting.  

Sorry if this seems obvious to people, but does this just sound like a cold joint somewhere or can a bad TL072 or 1N270 cause this kind of behavior? I've reflowed my wire to board joints and even added hot glue to stabilize them if they were somehow wiggling too much.

In summary: pedal needs to "warm" up on start up, pedal fades out then fades in when turned on from bypass, and pedal may be more prone to do this when I have the gain pot bypassed for full gain.

Any thoughts? Thanks!

[PRR]

It is hard to think about function with just a layout.

> The pedal's volume was too low when I built it

Find your "lost volume". Any bad solder joint. A red-red-orange resistor where should be red-red-red (or vice versa). Way-off voltages at transistor pins-- Q1 Q2 Q3 collectors should be near 4 Volts.

[mth5044]

I was looking for a schematic too. PRR - looks like what you linked to is a muff based thing. I think OP's circuit is more like a distortion +?

[Zounds!]

Sorry, I don't have a schematic for the pedal. It's supposed to be a highly modified Ross Distortion - http://gillcar.tripod.com/Files/Rosshem.jpg  .
I think the LSTR is a Big Muff-style deal. No transistors on this one, just 1N270 diodes and Tl072s

Several other people who posted in the comments on the vero layout also had low volume, so it may be part of the layout rather than a build error. It may have had to do with the tone stack -- unity gain is certainly available, but cutting the mids also cuts the volume a lot. I think all of BAT's pedals are supposed to have tons of output -- this certainly does not, but the output was fine right off the bat unless I scooped the mids. With the boost added on I can just scoop all the mids if I want to and still be above unity gain.

I don't actually mind my workaround, though I realize you're probably suggesting that the lower than volume could be tied in with the fade in/fade out of the signal...

[PRR]

> highly modified Ross Distortion

That's got just one opamp (working).

The BATQM layout has four opamps (2 duals) and appears to be using all of them.

Highly modified indeed.

With 82 legs on board and 18 off-board lines (hey, nice round 100!), I'm not inclined to decompose and understand what is really going on in there.

Basics which you are tired of hearing:

Solder Joints ! ! !
Wrong values
Right value in wrong place
The OUT pin of *most* opamps will usually sit near +4.5 Volts. There are exceptions, and in this case you may need clips or 3 hands to watch the voltage while you turn off/on and strum to excite the problem.

[Zounds!]

Thanks for the tips Paul. I am indeed tired of hearing them, which is why I definitely need to be reminded of them! 

I rewired the gain foot switch and used a new 3pdt but to no avail. I thought for sure that it was the 3pdt I was using, since everything is fine when the signal passes through the gain pot in "normal" mode, but then acts up only when I short out the gain pot. Nope!

Messed with it for a while to try to find the issue and noticed that it will sometimes act up after I've been playing for a while, without me even touching the foot switch. Often if I leave the effect on and set my guitar down for a minute, when I come back and strum a chord it does the same thing: swells up and then dips way down for several second before rising back to full volume. It's strange how it only does it on the full gain setting.

Was hoping someone had experienced these kinds of shenanigans before, either with a failing or overloaded (voltage too high? signal too hot?) diode or opamp, but looks like I'll be going back to troubleshooting 101. No easy answers, but thanks!