Dr Quacking problems

[R@bbiT]

Recently I built Dr Quack but when  I turned it  on it didn't quack. Sensitivity and range potz don't affect the signal.  Sensitivity pot affects the brighteness of the red led on the output of o-amp. So i cheched everything but with no results I didn't find any mistakes. Please help I know that someone of you know what's the problem!

Thank you

[Travis]

Check the standard things, orientaton/pinout of your transistor, same for the opamp.  

If all of that is OK, take voltages of the transistor and IC and report back.

Does the output LED turn off when no signal is applied top the circuit?
If it does, then:

What kind of signal are you running into the Dr. Q?  If the LED on the output is always on, you may simply have too much input signal.  The sens or attack pots may be broken/incorrect value, or may be miswired.  

If your guitar has a very high output, try a larger value sens or attack pots pot.

[R@bbiT]

The pinouts are correct, the led gous out when no input  signal, voltages are OK to my opinion. I have tried different o-amps and transistors, but it just Didn't work, but there is another thing: Bass mode doesnt work at all(when I switch to bass then there  is no output signal). This circuit leaves me with a feeling that it will never work.

[Paul Perry (Frostwave)]

This circuit leaves me with a feeling that it will never work.

Your comment leaves me witht the4 feeling that there is at least one (probably more) wiring errors. I've been there. Check each junction on the circuit & compare wiht the actual wiring.

[strungout]

I've built this circuit many times now. I just plain repopulated my project board twice cause I couldn't find anything worng with it, and funny enough it did work then (which has "wiring mistake(s)" written all over it

You said that the sens pot affects the brightness of the LED from the opamp, does it flash along with your playing when your guitar is plugged in? The other LED show always be lit up.

If you still can't find the problem, build an audio probe. It's a valuable debugging tool, you can follow the signal and hear if it's not going through a connection it should be going through.

[Mark Hammer]

Common sources of build problems with (and special to) the DQ/NQ:

1) FET or bipolar pinouts wrong.  Wrong FET pinout gets no audio signal at all, even when you play with the trimpot.  Bad bipolar pinout gets you audio output but no sweep.

2) LED orientation incorrect.  Audio output but no sweep, and no LED illumination when picking.

3) Insufficient gain in envelope follower stage.  Audio output, but minimal sweep and potentially very low default filter centre frequency (will sound very muffled).

Beyond this, there are the usual sources of build difficulty such as switches and pots with intermittent connections, overlooked obligatory ground connections on pots and other places and op-amps stuck in backwards.

The first time I made one using RG Keen's layout, I overlooked the fact that P-n-P layouts were the mirror image of traditional photo-etch layouts and made one backwards.  I had to bend the chip pins over, and re-orient all polarized components to get it to work....which it did, eventually.