Nurse quacky - no sound !

[alcoloic]

Hi everybody !
i already build a few fx (the easy one "jawari" "lofomofo" "greenringer") but now i'm having troubles with my nurse quacky ( http://www.generalguitargadgets.com/pdf/ggg_nurse_quacky.pdf ).
the leds work as describe ( one is on all the time and the other one react to my playin)
the sensitivity and the attack pots affects the way the blinkin led works
i triple checked the connections and soldering , the transistor pinout is respected but the only sound i get out of it is a low level gated/distorted sound that i only hear if i turm my amp really loud .
i don't have a 3m3 resistor so i used a combination of 2 resistor that make 3m4 resistor (but i don't think that's the problem since the led blink correctly )
also there's a hole missing in the pcb i bought from ggg (the "out" signal) so i soldered the wire at the back of the pcb on the corresponding lug of the 0,1uf cap (i also tried the 470k resistor but i get the same result)
i noticed that i get the same result (crappy low level sound) if i take the transistor off ( i guess that's a lead )
i'm a noob in electronic, so please don't hate
i used all the component used on the ggg pdf file ecxept for the 3m3 resistor
sorry my english is not really good
thanks in advance

Loïc Moreau

[Mark Hammer]

Donc, le problèm est identifié comme dans le filtre lui-même.  (So, the problem is identified as being in the filter itself)

Est ce que le chip est bien installé? Il se passe des fois qu'un ou deux des jambes devienent pliées au-dessous du chip.  Il semble que tout est en forme, mais on travail avec moin que tout les jambes.  (Is the chip properly installed?  It happens sometimes that one or two pins get bent underneath the chip.  It may look like everything is properly installed, but you're really working with less than all the pins.)

[solarplexus]

ahh bien je ne savais pas que tu parlais français Mark 

peut-être que tu as inversé la chip et qu'en appuyant le bypass tu l'a brûler!  Ça m'est déjà arriver et c'est frustrant!

Now in english :

maybe you reversed the chip, put it on and then fried it... happened to me once!

[alcoloic]

wow thanks for quick answer and the french translation ! ( wow merci pour la réponse rapide et la traduction francaise ! lol  )
i checked and none of the chip pins are bent so i guess that's not my problem
and btw i socketed the chip and the transistor so i doubt i fried those

Donc, le problèm est identifié comme dans le filtre lui-même.  (So, the problem is identified as being in the filter itself)

sorry if i sound silly but what are the component that make the filter itself and how could i check those ?

[Mark Hammer]

Un moitié du chip comprend la rectification (le moitié avec les LEDs), et l'autre comprend le filtre.

Dans ce tableau (http://www.home-wrecker.com/nurse-quacky.png) le moitié en haut est le filtre.  Si tu as un DMM, mesure le voltage au jonction des deux résisteurs de 470k (le jambe négatif).  Ça devrait être environs 50 et 150mv quand to jeux le guitarre.

[alcoloic]

Si tu as un DMM, mesure le voltage au jonction des deux résisteurs de 470k (le jambe négatif).  Ça devrait être environs 50 et 150mv quand to jeux le guitarre.

sorry i don't understand how to do that  ! could you explain ? i tried using my multimeter on the lugs of those resistors and i get  4,7 on ac mode and 3 on dc mode ( i obviously don't know how to use that thing ) and doesn't seem to change when play my guitare

[Mark Hammer]

Set it to a low AC range (e.g., 200mv).  Touch one probe to the IC pin, and the other to ground.  Now strum the guitar.

If the signal is reaching the op-amp input, then you should see about 50-100mvAC (more if you have hot pickups or strum hard).

Are the filter capacitors the correct value?  (4700pf = 4n7 = .0047uf)  If they are too high a value then the filter might be sweeping too far below the frequency range of the guitar.

[alcoloic]

yes i used 4700pf caps (those are mylar)
i tried measuring with my voltmeter (ac mode) betwen the box (ground) and all the pins of the chip (http://www.datasheetcatalog.com/datasheets_pdf/M/C/1/4/MC1458-D.shtml)
1=3,7v (up to 4,7 when i strum my guitar)
2=2,2 (2,1 when i strum my guitar)
3=3
4=0
5=9,4
6=9,8
7=3,7
8=20,1

[Mark Hammer]

The measured voltages are confusing.  Something is not right.

Let us call the op-amp in the top half of the schematic IC1a, and the bottom one IC1b.  If this is powered by a battery, you should read 9VDC on pin 8, 4.5VDC on pin 3 or 5 (whichever is used for the filter) and around 7.5vdc on pin 3 or 5 (whichever is used for the envelope follower). Ces sont des voltages DC.

If IC1a = pins 1-3, then the AC voltage at pin 1 should be just a tiny bit higher than the AC voltage at pin 2.  For any normal guitar plugged directly into the pedal, with the guitar volume up full, I would expect about at least 50millivoltsAC on pin 2 (but not much more than 200mv), and maybe 5-10mv more on pin 1.  Les voltages mesurés (2,2V et 3,7V) sont pas logiques.  De plus, pourquoi est-ce que le voltage à jambe 2 devien moin quand tu jeux?

Maybe the biggest ? is how you get 20,1V on pin 8.

Je pense que le façon dont t'a pris ses mesures n'est pas correct.

2me essai!

[alcoloic]

thanks for helping Mr Hammer !
i retried in dc mode and now i get :
1=2v ( 2,5 when i strum)
2=1,9 (1,7 when i strum ) wierd
3=1,7
4=0
5=4,7
6=4,8
7=2
8=9,5
( i'm using a power supply not a battery )

[Mark Hammer]

Okay.  The voltages that will be diagnostic are the DC voltages on pins 3, 5, and 8, and the AC voltages on mins 1, 2, 6, and 7.

You say the LEDs are behaving properly, so you should see around 35-100mv AC at pin 2 and a couple of volts AC at pin 1 when you strum (the 47k and 3.3M resistors produce a gain of around x70, so 100mv input becomes 7VAC output).

What is still not clear is whether the input to the filter stage (pin 6) is actually receiving a good input signal.  You should be able to see between 35-100millivolts AC at pin 2 when you strum.  So far, this has not been confirmed.

[alcoloic]

i get static 2,2v ac at pin 2
i tried switching the chip and still get the same result
thanks
Loïc

[alcoloic]

hi !
i rebuild the nurse quacky and it still doesn't produce sound (exept while measuring the ac voltage on pin6)!
those are the results i get now
dc voltages :
pin3 = 1,7v
pin5 = 4,9v
pin8 = 9,7v

ac voltages :
pin1 = 3,8 (4,5 when i strum)
pin2 = 2,3v
pin6 = 10v (when i do this test i get an unclean autowha sound !!! )
pin7 = 3,7v