SOLVED Parasit Darkadiator: Low Octave Setting=No Signal

[Ginsly]

I'm working my way through a stack of PedalPCB boards, and thanks to all of YOUR help they work great so far - modded, too!

At the end of last year I picked up a full Parasit Darkadiator kit from Small Bear since I love Fredrik's Sidescroller. Tackling it before the other PedalPCB projects.

All seemed fine, but the Octave switch in "up" mode (all subs I believe) passes no signal. I think the problem may also be affecting the Width knob in the other two (functioning) Octave switch settings. It's quite loud counterclockwise, but very quiet as Width is turned up.

I found a solder bridge on the 3pdt daughterboard and corrected that, but it didn't fix the problem. Maybe I damaged a component?

All 12 (!) transistors seemed to check out fine, and I checked the continuity of the transistor sockets too - all seems ok. I may pull them, though.

I tested another on/off/on switch for the Octave control, and the same thing happened.

Not sure where to go from here. The board looks a bit rough at this point, what with desoldering the Octave switch a couple times... White PCB doesn't help!

Hopefully it can be saved. Below is the schematic, but I'm not knowledgeable enough to know which components to look at/replace first when it comes to the Lower Octave/Subs part of the circuit.

I'd really, really appreciate any thoughts.

 

[comradehoser]

Pics of your build?

 

[Ginsly]

@comradehoser Thanks for chimin in! I’ll work on that, but honestly, nothing looks out of place. I think! Ha… It does however look pretty atrocious in places, due to desoldering a couple things. I’m a pretty new builder, and this is the first real issue I haven’t been able to solve.

 

[comradehoser]

It's essential to provide pics since user error is 99.99% of the time responsible for non-functioning boards, and often those errors are visible. Especially if it has your atrocity in it. PCBGuitarMania is an exception to this rule, but Parasit I have not heard anything poor about their circuits.

The next step is to do multimeter probes of continuity and voltage and to post your readings. I also find audio probes very useful. You may also want to look up demos or see in other forums if anyone else has built the pedal and if it exhibits similar behavior to what you're describing. I have built pedals where I think something is deficient when I have actually built it correctly and it's just the way it sounds.

 

[Ginsly]

@comradehoser Thanks again for offering your help - I heard from Fredrik of Parasit and he recommended switching to 2N2222's for a couple transistors - which worked! Replacing one brought the lower octave to life, and replacing a couple others raised the level of part of the circuit that was also quite low (part of of the Pulse Width pot's travel). Evidently the 2N3904s weren't cuttin it in a few places. I'm not sure if it's 100% optimal, but it sure does sound great now!

 

[comradehoser]

Rad! Mark the thread solved.

 

[gerryk]

@comradehoser Thanks again for offering your help - I heard from Fredrik of Parasit and he recommended switching to 2N2222's for a couple transistors - which worked! Replacing one brought the lower octave to life, and replacing a couple others raised the level of part of the circuit that was also quite low (part of of the Pulse Width pot's travel). Evidently the 2N3904s weren't cuttin it in a few places. I'm not sure if it's 100% optimal, but it sure does sound great now!

can I ask which transistors you swapped? having a similar issue

 

[Ginsly]

@gerryk sorry to hear, but kinda glad I’m not alone! Ha…

I’ll open it up and let you know which ones I swapped. Back atcha shortly.

 

[Ginsly]

@gerryk In order to get it working optimally, I replaced the 2N3904s with 2N2222As in these locations:

-Top right bank of three transistors, close to the Octave pot lugs: replaced the top left one.

-Lower right bank of three transistors, close to the Volume pot lugs: replaced all three transistors.

The one near the Octave pot helped with the Lower Octave, but I still had issues with very low volume through most of the Pulse Width knob. In order to even that out I had to change all three transistors in the lower right near the Volume pot. Hope it works for you!

Was this a kit or just a board? I got a whole kit from Small Bear last Dec, figured I'd ask...