Parenthesis 2020 missing octave

[bobson dugnutt]

Just finished up this parenthesis build...the overdrive and boost sound massive, and I'm really pleased there, but the octave is completely absent when it's engaged.

Here's the symptoms:
- Everything but the octave bypassed: only the guitar's dry sound is coming through
- Distortion and octave engaged: no sound at all!
- Even with the octave disengaged, turning the octave knob down almost all the way will kill the output.

For D1 and D2 I went with the 1N270, since it was one of the only GE diodes readily available on Tayda. There's a decent number of threads with other people having octave issues, but I haven't run across any threads with symptoms like this.

Any ideas? I'm 90% sure I installed these diodes the right direction, but maybe I'm misunderstanding these GE diodes.

Thanks in advance!

 

[Nostradoomus]

You might have a bum switch, try desoldering the switch and installing the jumper indicated in the build doc. It’s a quick test!

 

[bobson dugnutt]

Smart! I'll give that a go this evening. Totally forgot about the jumper.

 

[Nostradoomus]

If that yields nothing get the DMM out and record your Q2-4 voltages. I don’t think any diodes from Tayda are legit GE but that shouldnt stop it from working unless they are straight up bunk. I used 1n5817 in mine, be sure to try and match them for Vf.

 

[bobson dugnutt]

Thanks so much for all the advice! I tried the jumper to no avail. In the process of disassembling everything (it's a tight fit!) I somehow managed to make matters worse and now no signal passes through when it's bypassed. Doesn't seem to be a loose connection anywhere; I need to do more continuity tests. Still debugging but will probably shelve this specific build for a few weeks to avoid ripping my hair out further.

I have another one of these I'm building in the not too distant future for a friend so I'll heed your diode advice and see if I learned anything from this mess

 

[Nostradoomus]

While you’ve got it out snap a picture of the solder side

 

[bobson dugnutt]

Here's the carnage. Peeked behind the pots as well and haven't seen any obvious cold solder joints but I'm curious if y'all spot anything!

 

[bobson dugnutt]

An update on this one: I finally worked up the courage to take another swing at it. So close yet so far.

I've replaced the octave diodes with some soviet D9Es from (what I think) is a reputable supplier. This time around, though, I also took the time to match the voltages. Assuming I'm measuring them correctly, I'm seeing ~0.251V for each one. Also went through and cleaned up the connections and the fuzz and boost stages work great!

The octave, however, is acting up. Exact same symptoms as before: with only the octave engaged, no matter where the octave blend is set I only get the clean guitar signal. With the octave and distortion engaged no signal passes at all.

I have to get back to work, but I'm hoping to do a deeper audit of it tonight. I'm curious what y'all think of those diode voltages and if there's any suggestions on debugging strategies from here, since I'm pretty much out of ideas at this point. Worst case, I have another PCB of this I was going to build for a friend, so I'll build that and see what happens.

Thanks so much! Y'all are the best for helping debug this!