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This is not my first build but is my first modulation build. Finally got all the parts needed to put it together minus an enclosure. decided to wire it up to see if i could get it working. I’ve done about 6 pedals so far but they have all been fuzz/overdrive/preamp pedals, so the stages of the pedals were much easier to follow and had far less parts.
anyways on to my problem, led lights up, everything seems to be getting voltage that should. audio bypass works, when the pedal is on the audio still plays but there’s no chorus effect. No part substitutions. i double checked the restistors and capacitor values. everything seemed correct. I did use the 3207 chip, I believe that’s why the voltage on pin 1 is 0. The pins are jumpered the correct direction. I did it under the IC because there didn’t seem to be any issues since the socket lifts the IC up so high.
The only problems i’ve run into on my other builds were a bad capacitor and a joint that solder didn’t flow into properly. I’ve tried to reflow any joints that looked suspect. checked for voltage on all the capacitors and resistors around the transistors and i’m coming up blank. everything seems fine.
transistor voltages are way off from what i saw on other posts though. voltage in was 8.97 from a danalectro 9 volt ac adapter. it has worked with all my other builds for testing.
ic1
1. 4.38
2 4.39
3. 3.49
4. 0
5. 4.23
6. 4.35
7. 4.32
8. 8.69ic2
1. 0
2. 4.02
3. 7.19
4. 7.7
5. 8.07
6. 4.02
7. 7.81
8. 7.82ic3
1. 7.94
2. 0.07
3. 7.07
4. 8.07
5. 8.07
6. 8.07
7. 0
8. 0
9. 0
10. 4.01
11. 4.02
12. 0
13. 7.95
14. 8.07ic4
1. 1.65
2. 3.93
3. 3.64
4. 0
5. 2
6. 2
7. 3.7
8. 8.6q1
e. 6.9
b. 6.1
c. 0q2
e. 7
b. 7
c. 8.6q3
e. 8
b. 8.5
c. 8.6I tried to follow the schematic to see what was around the transistors that could be bad or accidentally grounded but this schematic is far more complex than the fuzzes and overdrives i’ve worked with so far. when i had a bad capacitor in a previous build there was a point in the circuit where nothing after it had voltage. Similar with the bad solder joint. parts of the circuit after that didn’t have voltage. I’m not finding anything like that with this build.
I don’t have an audio probe yet. I still need to make one.
Let me know if you have any ides of what it could be.
Have you tried adjusting the trimmer in VERY small increments? I’ve built a few Mini-Me circuits and always start with that trimmer set at noon and ever so slowly, in small increments, start turning it clockwise till I get the best chorus effect.
HAH!!!
So I hooked it back up to adjust the trim and there was in spot in its range where I was noticing some popping. Flip the pcb over and one of the pots wires had broken . Trimmed, stripped and re-soldered that wire. Hooked it back up and all of a sudden it’s alive!
From the other threads on the mini me I read it sounded like around 1 o’clock was the sweet spot the trim knob. For my build it was closer to 11 o’clock. Do you think that’s due to the use of the 3207 chip or just part tolerances?
I also found it very strange that if the trim knob has such a small area where it works and is almost like an on/off switch and not gradual like the trim in my fuzz face clone.
You’re biasing the input of the BBD, even the same type of IC may bias slightly differently
If you don’t bias it correctly you may get distorted output or no output at all, internally it’s a number of stages, connected capacitors and switching transistors / FETs which require correct DC biasing to work as intended like a fuzz face if you bias the transistor incorrectly you’ll get sputtering output you may have a greater range but you’re trying to achieve different outputs distorted or as clean as possible
Obviously it’s a tad more complex than that you’ve other things to consider like externally connected components clock frequency etc but it’s basically the same thing to get it to work the way you want
Here’s an article from the great Mark Hammer page 4 for biasing info
https://www.premierguitar.com/articles/25035-behind-the-bucket-brigade
ProfBio – glad to learn you’ve sorted it out. And regarding trimpots . . . they will behave differently in different circuits. For most BBD builds, there is a tiny sweet spot – but for fuzzes & many other dirt pedals, there tends to be a larger range. In your case of an 11:00 setting, it may be due to supporting component tolerance differences.
Happy building!
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