SOLVED Circulator Output Low

DSpenceATL

New member
Hello all,

I have exhausted my options with this build, so I think I’m in need of some fresh eyes and ideas.

I’ve completed a circulator build, and everything seems mostly normal, except that the output is well below unity volume. I’ve gone through it with an audio probe and identified that the signal becomes quieter at all of the 1.2k resistors (R8, R12, etc.)

I’ve done a reflow, scrub down with 99% alcohol, tested and tested and tested, and gone over this thing with a bright light and a magnifier looking for issues. I’m sure it’s right under my nose, but I think I need some outside perspective.

Recorded voltages follow
Non-Vref voltages are average, they move around a little bit in a small range.
IC3 voltages presented as a range are swinging wildly so I just posted the top and bottom.

IC1
1 1.23
2 1.55
3 4.55
4 4.55
5 5.67
6 -
7 5.71
8 4.55
9 4.55
10 5.73
11 9.12
12 5.66
13 4.54
14 4.55
15 1.52
16 1.13

IC2
1 1.19
2 1.59
3 4.55
4 4.55
5 5.71
6 -
7 5.68
8 4.55
9 4.55
10 5.68
11 9.12
12 5.68
13 4.55
14 4.55
15 1.18
16 1.15

IC3
1 1.21
2 0.71
3 1-6v
4 1.96
4 2-4.5v
5 2-4.5v
6 -
7 2-4.5v
8 2-4.5v
9 2-6.5v
10 2-6.5v
11 9.12
12 2-6.5v
13 2-3v
14 2-6.5v
15 0.81
16 0.87

IC4
1 4.55
2 4.55
3 4.14
4 -
5 4.55
6 4.55
7 4.55
8 9.12

IC5
1 4.55
2 4.55
3 4.55
4 -
5 4.55
6 4.55
7 4.55
8 9.12

Apologies for the somewhat messy PCB, it’s definitely not as clean as when I built it due to so much troubleshooting. Ignore the yellow wires, they were thrown on in a hurry because the solid core ribbon cable broke from too much handling while troubleshooting.
 

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I just put this one together yesterday and tested. I’ll check my IC3 voltages and compare.
Do you have the jacks wired?
It looks like one of those pots need insulating.
 
I just put this one together yesterday and tested. I’ll check my IC3 voltages and compare.
Do you have the jacks wired?
It looks like one of those pots need insulating.
That would be great, thanks!

I had the jacks wired but removed the whole thing from the enclosure and put it on my auditorium for testing.
 
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IC1
1: 1.21v
2: 480mv
3: 4.37v
4: 4.37v
5: 5.46v
6: GND
7: 5.46v
8: 5.46v
9: 4.36v
10: 5.46v
11: 8.74v
12: 5.46v
13: 4.36v
14: 4.36v
15: 600mv
16: 1.21v

IC2
1: 1.21v
2: 680mv
3: 4.36v
4: 4.36v
5: 5.46v
6: GND
7: 5.46v
8: 5.36v
9: 4.36v
10: 5.46v
11: 8.74v
12: 5.46v
13: 4.36v
14: 4.36v
15: 510mv
16: 1.16v

IC3
1: 1.20v
2: 500mv
3: 1.06v - 5.83v
4: 1.42v -3.70v
5: 2.42v - 4.85v
6: GND
7: 2.42v - 4.85v
8: 1.39v - 3.70v
9: 820mv - 6.28v
10: 820mv - 6.28v
11: 8.74v
12: 820mv - 6.28v
13: 1.42v - 3.70v
14: 1.06v - 5.83v
15: 220mv - 448mv
16: 1.23v

Question: There are four 1uF film caps (C7,9,10,11). Have you verified these? Also, C8 (100pF)
 
IC1
1: 1.21v
2: 480mv
3: 4.37v
4: 4.37v
5: 5.46v
6: GND
7: 5.46v
8: 5.46v
9: 4.36v
10: 5.46v
11: 8.74v
12: 5.46v
13: 4.36v
14: 4.36v
15: 600mv
16: 1.21v

IC2
1: 1.21v
2: 680mv
3: 4.36v
4: 4.36v
5: 5.46v
6: GND
7: 5.46v
8: 5.36v
9: 4.36v
10: 5.46v
11: 8.74v
12: 5.46v
13: 4.36v
14: 4.36v
15: 510mv
16: 1.16v

IC3
1: 1.20v
2: 500mv
3: 1.06v - 5.83v
4: 1.42v -3.70v
5: 2.42v - 4.85v
6: GND
7: 2.42v - 4.85v
8: 1.39v - 3.70v
9: 820mv - 6.28v
10: 820mv - 6.28v
11: 8.74v
12: 820mv - 6.28v
13: 1.42v - 3.70v
14: 1.06v - 5.83v
15: 220mv - 448mv
16: 1.23v

Question: There are four 1uF film caps (C7,9,10,11). Have you verified these? Also, C8 (100pF)
Oh my god. I have checked this like 4 times, but you asking forced me to check again, and I have 1000 PF caps installed, thinking this whole time they were 1000 NF. I am facepalming so hard right now.
 
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Confirmed! Having the correct values does in fact cause the pedal to function as intended!

To anyone stumbling upon this thread 5 years from now, definitely double check those 1uf caps.
 
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