nurse quacky = no quack :(

[elfito]

hi!!

i build the nurse quacky but its not quackyng, when i switch it to the circuit it has low volume and it does not quack, the LED lights when i play the guitar but the pots dont do anything

any idea on what will cause this

[anchovie]

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[Mark Hammer]

There are 2 LEDs.  One is always on, but does not signify anything other than that current is flowing through it.  The other may light up briefly when you play, but that would depend on both the inherent brightness of that LED, the gain of the op-amp preceding it, it's proper orientation, and the strength of your playing.

If you have a meter, measure the AC voltage at the output of the op-amp before it.  It ought to be in the 500mv to 2v range when you play.  Now measure the voltage on the other side of that LED.  The LED will subtract 1.5V from the op-amp output, so what you measure will not be as substantial as what you get out of the op-amp.  You should, however, be able to measure some varying DC voltage there, even if the LED does not light up in any observable fashion.

To determine whether the filter section itself is functioning as nature intended, temporarily wire up a variable resistance of 100k or so in parallel with the 47k resistor to ground from the junction of the two .0047uf filter capacitors.  The envelope-detection portion of the circuit and the accompanying transistor merely serve to present a changing resistance to ground in parallel with the 47k to change the centre-frequency of the filter.  If you can make that centre-frequency change by varying the resistance to ground in any fashion - whether automatic or manually - then you know the filter works, at least.

[elfito]

the only value i change was the 25k pot ,i used a 50k pot

[elfito]

keep trying to get the quak without any luck
i wire a 100k resistor to the 0047uF caps and i tried on all 47k resistors but no quack came out (i jumped it to the pin 1 on the IC and got a cool fuzz tone that can be controled by the 100k pot) the volume is fine now,BUT I WANT THE QUACK

[cathexis]

I didn't get mine to work right until I used a different opamp than the one specified. Search the forum, that's where I got the suggestions for choice of opamp. Unfortunately I gave mine away, so I can't check what I used, and I don't remember. It sounded great, though.
LARS

[doc_drop]

I had the same experience with the op amp. I replaced the TL072 with a NE5532. That did the trick, and I love this quacker! Give it a shot.

[elfito]

finaly got it to quack
but the controls are bad but im prety sure its because of the pot i use(they are cheap)so i'm gonna get some good pots

[doc_drop]

finaly got it to quack

Just out of curiosity, what did you do to get it to work? Did you replace the op amp?

[elfito]

i redo the perfboard layout and that worked
i also tried other IC's but only the TL072 quacks,the mc1458 make fuzz sounds and the NE 5532 does nothing