# old Octagon input distortion



## Dice1012 (Mar 14, 2021)

Getting some overloading/distortion on the input of this older Octagon build, where should I be looking? Could not find the old schematic. Could this be a resistor problem? Everything works fine just a overload when the strings are hit hard.


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## Cybercow (Mar 15, 2021)

Did this suddenly start happening? Does it do it by itself, or is it somewhere in the middle of a pedal-chain? If in the middle, what's before it? Are the pickups on your guitar active?


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## Robert (Mar 15, 2021)

This should be the build doc for that version:
https://docs.pedalpcb.com/project/Octagon.pdf


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## Dice1012 (Mar 15, 2021)

Cybercow said:


> Did this suddenly start happening? Does it do it by itself, or is it somewhere in the middle of a pedal-chain? If in the middle, what's before it? Are the pickups on your guitar active?


No, has been this way since I built it. 
Built 2 others at the same time, those are fine, but have 1% resistors. Ran out and used some 5% nothing one. That is the only difference. Would a resistor near the input be the problem?


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## Robert (Mar 15, 2021)

I doubt 5% tolerance is causing an issue, but an incorrect value would.


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## Dice1012 (Mar 15, 2021)

Cybercow said:


> Did this suddenly start happening? Does it do it by itself, or is it somewhere in the middle of a pedal-chain? If in the middle, what's before it? Are the pickups on your guitar active?


No, has been this way since I built it.
Built 2 others at the same time, those are fine, but have 1% resistors. Ran out and used some 5% nothing one. That is the only difference. Would a resistor near the input be the problem
Passive pickups.
Only pedal.


Dice1012 said:


> No, has been this way since I built it.
> Built 2 others at the same time, those are fine, but have 1% resistors. Ran out and used some 5% nothing one. That is the only difference. Would a resistor near the input be the proble
> 
> 
> ...


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## Dice1012 (Mar 15, 2021)

Robert said:


> I doubt 5% tolerance is causing an issue, but an incorrect value would.


Any idea which one?


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## Cybercow (Mar 17, 2021)

Seeing as you have two others that work fine, have you tried comparing voltage measurements on IC1? Have you tried swapping out the TL072 (IC1) opamp? If that doesn't solve it, I would go thru the trouble of lifting one leg of each of those 5% resistors, measure them and check them against the BOM values. If the 5% resistors match the BOM are within their rated tolerance, they should be just fine. If the problem still persists, you may want to use an audio probe on the it and compare audio probing between the bad one and one that works right.


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