SOLVED Aion Refractor (Klon) large volume difference On/Bypassed

[Rpschultz13]

I've built 3 Aion Refractors. First one worked great (amazing pedal). 2nd one didn't at all (troubleshot for weeks). 3rd one kinda works, but there is a large gain difference between ON and Bypassed. More noticeable in Buffered mode obviously, but still there in TB.

I have double checked polarity on diodes and electrolytic caps, and checked ALL the resistor color codes. To me this sounds like I put in the wrong gain resistors for the gain stages, but those are (seem) correct. Of note, I used a 1u MMLC for C16 instead of tantalum, shouldn't matter. And the "magic" diodes are socketed.

I've built dozens of pedals, not sure why I have trouble with this one.

Suggestions?

 

[Caedarn]

I’m no troubleshooting expert by any stretch. It’s probably just the lighting in the photo but I don’t see any solder on one leg of C8 or C13?

 

[jimilee]

Time to break out the audio probe and start at the end and work backwards.

 

[PJS]

Can you be a bit more specific? I am assuming that the low volume is when the pedal in engaged? Is that correct? Also, the gain knob. Does it work as intended or more like a volume knob?

 

[Rpschultz13]

Yes the volume and gain work. And yes it’s much quieter when engaged than when bypassed.

 

[PJS]

OK. It is not certain, but I would be looking for the problem between R16 and the output. It might be earlier in the circuit but I would think the end part is more likely. First steps are checking the voltages on the op amps, checking component values, checking for bad solder/shorts. If that all checks out then I would be using an audio probe to follow through and see where the volume decreases and look there for the problem.

 

[szukalski]

 

[Rpschultz13]

OK. It is not certain, but I would be looking for the problem between R16 and the output. It might be earlier in the circuit but I would think the end part is more likely. First steps are checking the voltages on the op amps, checking component values, checking for bad solder/shorts. If that all checks out then I would be using an audio probe to follow through and see where the volume decreases and look there for the problem.

You are spot on. Before R16 I get a nice strong signal. But the junction between R16 and IC2APin2, I get nothing. Then on IC2APin1, I get a faint signal. So C12, R17, R18? Or possibly R7, R19 or C16, that's the tantalum cap that I replaced with an electrolytic?
I should note the volume pot does work a little, but the gain pot doesn't do anything.

 

[Rpschultz13]

It was R20! I had 392R instead of 392k. What oddball sizes, I'm shocked I had both. I made the same mistake on a previous build. I checked the color codes of all the resistor and the Orange White Red was right, just missed the multiplier.