Dr. Quack problem. Any ideas?

[markr04]

Hi all. I built a Dr. Quack. I've built a few things prior to this, so I'm not completely new to it. Problem is very, very low output. There are two LEDs. One comes on and stays on when the board gets power. The other, I've discovered, blinks as the effect works. The only way I can get enough signal to hear anything or make the LED blink is to insert the input plug 1/2-way instead of all the way - in other words, both ground and signal are going to the board input (I think). I'm testing this without any of the switches, so that's not the problem here.


schematic:
http://www.muzique.com/schem/quack.gif

PCB (the way I built it):
http://www.generalguitargadgets.com/diagrams/dr_quack_lo.pdf

Any thoughts/input would be greatly appreciated.

Pulling my hair out,
Mark

[vdm]

i know it probably sounds really obvious, but are you sure your wiring on the input jack is correct??? it could be that you have the tip and sleeve mixed up and the really low output is because the power supply isnt connected at all, and signal is just being pushed through from the guitar.

That would explain the 'half way in' jack thing - but do the lights come on when it is in halfway??

have a really hard look at how these wires are connected and what does what - i spent about a month trying to figure this out on my pedals!!!

trent

[niftydog]

it's no good just "guessing" about what's connected to what. Insert that jack and test it with a multimeter. You have to be definitively assured of that before you can move onto the next step.

Besides, shorting signal and ground together will result in NO signal at all. So that's not your problem.

Sounds to me like your input jack is incorrectly wired though. The circuit obviously works, so double check your jack wiring again. Possibly you have the tip and ring connections mixed up or something.

[RobB]

Yes, check what niftydog and vdm have suggested.  

I'm testing this without any of the switches, so that's not the problem here.

Without a bypass switch, the sleave should go to pad 1, ring to pad 9 and tip to pad 2.  If these things are correct then the unit should turn on and the guitar signal should be delivered to the 0.05uf input capacitor.  If you’re using sockets with exposed contacts this should be easy to check.  
I’ve just noticed the 4M7 resistor is not included in the schematic but that doesn’t matter.

[cbriere]

Hi,
My experience of this kind of effect (touch wha..) has lead me to experience and i have came up with a pedal i named
HIPWAH. This circuit has also auto-wha with adjustable
depth and center frequency.
You check my site to ear sample sounds.
And check the schematics, see if it's look
familiar to you.

http://pages.infinit.net/cbriere

again, it's just a suggestion, you maybe want
to continue with what you have done and it's ok.

[Torchy]

Sounds like you have tip & ring swapped on the socket.

Ive built 4 of these so far using my current vero layout & 3 previous attempts. All had low output. IME this circuit is NOT happy with "any" dual op-amp, and will have low output unless you use a 1458 or 1558 dual op-amp. Using a 1458 all got all 4 working ok. Previously I tried TL062/072/082/4558/LF353 and they all suffered from low output - dunno why :?

[Mark Hammer]

Hi,
My experience of this kind of effect (touch wha..) has lead me to experience and i have came up with a pedal i named
HIPWAH. This circuit has also auto-wha with adjustable
depth and center frequency.
You check my site to ear sample sounds.
And check the schematics, see if it's look
familiar to you.

http://pages.infinit.net/cbriere

again, it's just a suggestion, you maybe want
to continue with what you have done and it's ok.

Je suis très impressioné.  Considerons une autre option.  Le pédale "Hypnoflange" de Rocktron a un LFO qui ajoute un voltage AC qui est tres lente, assez lente de semble comme un voltage DC.  En effet, ça change le gamme du "sweep" constamment.  Est-ce que c'est possible de combiner les deux - envelope et oscillateur tres lente - en même temp, et d'ajuster l'equilibre entre les deux?  Je connais que le pédale "Auto-Q" de MXR/Dunlop est capable de le faire, mais je crios que le game de l'LFO est trop vite de faire ce que je suggére.