Parenthesis octave issue

[Insidecircles]

I've built two parentheses circuits and they both have the same problem: with the octave engaged, the volume drops as you turn up the octave blend (with no noticeable octave effect).

This sounds like the same issue that was covered in this thread: https://forum.pedalpcb.com/threads/parenthesis-octave-problem.1133/ I'm posting a new thread here as that conversation solved the OP's issue, and my issue sounds like it has a different cause.

R18 and R19 are the correct values (47k and 470k, respectively).

Some (hopefully) relevant measurements:

Q2. C, 9.12V. B, 43mV. E, 320mV
Q3. C,1.99V. B,6.38V. E, 7.10V
Q4. C, 6.37V. B, 780mV. E, 260mV

Ge diodes (1N34As, same reading for each):
cathode: 4.05V
anode: 47mV

Any thoughts about what my issue might be? Q2 doesn't look right... perhaps something up with the diodes? Not leaky enough?

 

[lnhrc]

I just had same issue. The polarity of D2 and D3 is screen printed wrong. I swapped them both round and now the octave works. However after doing this, the rat started playing up when it was working perfectly before. Let me know what happens after you make that swap! ie if you have rat issues.

 

[lnhrc]

This was info I got on another thread. I’m tearing get my hair out now as I can’t figure what is going on :-/. Pedal pcb mentioned something about clipping led polarity rather than the diodes so I’m stumped.

 

[JetFixxxer]

I've built two parentheses circuits and they both have the same problem: with the octave engaged, the volume drops as you turn up the octave blend (with no noticeable octave effect).

This sounds like the same issue that was covered in this thread: https://forum.pedalpcb.com/threads/parenthesis-octave-problem.1133/ I'm posting a new thread here as that conversation solved the OP's issue, and my issue sounds like it has a different cause.

R18 and R19 are the correct values (47k and 470k, respectively).

Some (hopefully) relevant measurements:

Q2. C, 9.12V. B, 43mV. E, 320mV
Q3. C,1.99V. B,6.38V. E, 7.10V
Q4. C, 6.37V. B, 780mV. E, 260mV

Ge diodes (1N34As, same reading for each):
cathode: 4.05V
anode: 47mV

Any thoughts about what my issue might be? Q2 doesn't look right... perhaps something up with the diodes? Not leaky enough?

Make sure you check R18 and make sure it's the correct value. I had the exact same issue and I went through the schematic/drawings several times. When someone suggested check the value. I verified the value several times and my verification was wrong because I had a 4K7k not a 47k. After going bat shit crazy trying to figure out why my octave didn't work. The light bulb finally went off and I put the correct value and now it works as it should.

Looks like there is a bridge between the wires on your OCTAVE Switch. Also D6 doesn't look soldered into place.

 

[Robert]

The silkscreen for the clipping diodes is not backwards.

On one batch of boards the A/K designators for D6 (the 3mm red clipping LED) were reversed. This is the only diode silkscreen that was ever printed incorrectly. The PCB layout was correct, so as long as you install the Cathode of the LED into the Square pad you're good to go, regardless of the silkscreen error.

This has been mixed up with the confusion about the orientation of the germanium diodes in the original pedal....

Here's how that went:

On the original pedal the silkscreen is oriented the way you would normally install diodes in a Green Ringer circuit, and the diodes were installed accordingly...

The confusing part is that the original diodes are not silicon diodes, they are germanium and the stripe is on the Anode, not the Cathode like a traditional diode.... So technically in the original the diodes are installed backwards compared to a "normal" Green Ringer. It is unknown if this was intentional, or an error during assembly.

On the Parentheses Fuzz the silkscreen is oriented correctly, with the stripe on the Cathode end... (opposite to the Green Ringer, to match the original)

For what it's worth, I've swapped the diodes around both ways and the octave was still present in both cases.

 

[Nostradoomus]

On my parentheses mini I had some D9e diodes in there the way it was printed and didn’t get much. Swapped them out with some reversed 1n5817 (again ) matched at 235mv drop and OCTAVE CITY. I didn’t try them the proper way around because it sounds awesome now. Getting octave with my bridge pickup

 

[DGWVI]

I only get octave in my Parentheses and Fuzzdog Death Mini when the diodes (silicon) are installed opposite the screen print. Otherwise it just seems to act as a sort of filtered gain stage, but definitely doesn't have a pronounced octave

 

[Nostradoomus]

I think I might do a flip flop of diodes on a switch as I do enjoy that extra textural gain you get with them the other way around.

 

[Chuck D. Bones]

Q2 has inadequate bias. Emitter should be closer to 4V. This crazy circuit depends on leakage in D2 & D3 and high hFE in Q2 for correct biasing. either D2 & D3 aren't leaking enough (likely) or Q2's hFE is too low (less likely). Don't bother trying to measure Q2-B, your DMM loads down the circuit and gives a false reading. FYI, most of the 1N34A's in circulation are fugazi. Many are actually Schottky. They don't have to be 1N34A in this circuit, but they do have to be Ge for it to work as intended.

 

[Insidecircles]

Thanks all.

I'm going to socket the diodes. Try what I have the other way round, and also try some other GEs I have on order.

 

[silentrecords]

http://guitar-fx-layouts.42897.x6.nabble.com/file/n12089/russian_diode_chart.jpg

 

[silentrecords]

on Russian diodes the anode is marked with a stripe, the cathode is not - this is opposite to how most diodes are marked