Need help with zombie chorus (NO SOUND)

[jamal]

As per the instructions in the "DEBUGGING - What to do when it doesn't work" topic, here is my problem:

1.What does it do, not do, and sound like?
When everything is turned on (guitar connected to pedal and pedal to amp), the pedal's led turns on, but there is no sound coming out of the amplifier, only a mild hum.

2.Name of the circuit = Zombie Chorus

3.Source of the circuit (URL of schematic or project) = http://tagboardeffects.blogspot.pt/2013/02/zombie-chorus.html
(I built the one tagged as: "original version")

4.Any modifications to the circuit? No

5.Any parts substitutions? None (I had the luck of finding the MN3007 on a local electronics store)

6.Positive ground to negative ground conversion?
I do not  know what this is, I just followed the schematics.

7.
Battery voltage: 9.15 V

Not set up to turn the battery power on only when the jack is plugged in.

IC1(MN3007)
P1 = 9.21 V
P2 = 4.34 V
P3 = 5.02 V
P4 = 0 V
P5 = 0 V
P6 = 4.61 V
P7 = 4.34 V
P8 = 4.34 V

IC2(CD4046)
P1 = 0 V
P2 = 4.34 V
P3 = 4.61 V
P4 = 4.60 V
P5 = 0 V
P6 = 1.04 V
P7 = 1.04 V
P8 = 0 V
P9 = 4.4 - 4.7 V (The value varies within this interval, the same applies to other pins where an interval is shown)
P10 = 3.3 - 3.5 V
P11 = 3.3 - 3.5 V
P12 = 7.15 V
P13 = 0 V
P14 = 9.19 V
P15 = 0 V
P16 = 9.2 V

IC3(TL062)
P1 = 5.50 V
P2 = 5.00 V
P3 = 0.43 V
P4 = 0 V
P5 = 4.3 - 4.8 V
P6 = 4.3 - 4.8 V
P7 = 4.3 - 4.8 V
P8 = 9.17 V

IC4(TL062)
P1 = 3.3 - 5.5 V
P2 = 0.96 V
P3 = 4.4 - 4.7 V
P4 = 0 V
P5 = 3.3 - 6 V
P6 = 4.4 - 4.6 V
P7 = 1.3 - 7 V(It isn't a mistake)
P8 = 9.16 V
(All measured with the black probe connected to ground and red probe in each pin)

Other observations:
Since this is only my second diy-pedal, I think I should describe how I connected the off-board components. All the potentiometers, switch (SPST), LED(anode), input and output are wired as per the schematic instruction. Where it says ground, I connected the (-) wire from the battery clip. I then soldered both jack's grounds and the LED (-) lead to the highlighted positions below and connected them to the ground ((-) from the battery clip). (note that the board I used as individual pads for each hole, so the ground wires coming from the jacks and the (-) lead of the LED do not make contact with the components that are in the same horizontal line)


Could someone please help me solve my problem?
Thanks

[anchovie]

Pin 3 of IC3 should be about 5 volts - the 10M resistor should have similar at the other end too, along with everything else on that row from the left hand edge to the cut.

[jamal]

Well, on the other side of the 10M resistor he voltage is aprox. 5V, and on the other end (the one that's in the same lane as the tl062) it's 0.43 . Isn't the function of a resistor to drop the voltage?
Sorry, I'm still on the process of learning the basics.

[jamal]

So what should I do, could anybody please help?

[Buzz]

Maybe if you post up a couple of photos. Showing the front and back of the board. Also off board connections.

There may be something visible to fresh eyes that you have missed.

[anchovie]

Well, on the other side of the 10M resistor he voltage is aprox. 5V, and on the other end (the one that's in the same lane as the tl062) it's 0.43 . Isn't the function of a resistor to drop the voltage?
Sorry, I'm still on the process of learning the basics.

Not always. In this case it's connecting a bias voltage to the op-amp input so it needs to be high enough to give a decent input impedance and not pull a portion of your guitar signal out of the audio path.

10M does seem very high compared to what's usually seen in this configuration - try something from 470K to 1M.

[jamal]

Sorry guys, I just found out that I swapped the 2.2 nF capacitor with the 220pF one. I'll see if that does it.

[jamal]

Ok so now when I touch the input jack with my finger(and the output jack is connected to the amplifier) I can hear a loud noise coming out of the amplifier. However, when i connect the input jack to the guitar, there's still no sound coming out. Any ideas? I'll try to post some pictures. BTW, It isn't in a box.

[jamal]

P.S. I checked both guitar cables and they're working well

[duck_arse]

the pin3 volts on the IC3(tl062) are not problematic, maybe suffering from the "meter loading" effect on the 10M. as the output is correct, the input volts are most likely also correct.

search hereabouts for the "how to do audio probe", and apply same to circuit. also show photos.

[jamal]

Pics:
http://tinypic.com/r/wuhr14/8
http://tinypic.com/r/2uhmmtg/8
http://tinypic.com/r/15eu0z5/8
http://tinypic.com/r/2wc1ly8/8
http://tinypic.com/r/oawsow/8
http://tinypic.com/r/s5zj9c/8
http://tinypic.com/r/1zfpl02/8
http://tinypic.com/r/2s6sign/8
http://tinypic.com/r/2vi0akn/8

I tried the audio probe on the outputand it gave me a constant ticking sound.

[anotherjim]

I recommend checking against the schematic...
http://www.hollis.co.uk/john/zombie.jpg
The 10Meg resistor on the input pin3 is possdibly a typo. I think it should be 1Meg, and it is on other versions of the scheme, but I doubt it's the cause of no sound. The voltage on pin1 should depend on the bias preset, this is critical for setting the optimum signal path thru the MN3007.

I would suggest taking the MN3007 out of it's socket and fit a solid wire or low value resistor (<1K) connecting the socket pin 3 to pin 8.
If you still have no sound - it's nothing to do with the BBD chip and you should find the trouble spot with a probe.

[jamal]

well, I tried bypassing the mn3007 like you said but still no sound. So i guess my next question would be: how do I know what I have to probe?

[anotherjim]

Ok, you need a signal source feeding the input, then listen for it from the input, to the output of the first amp to pin 3 of the 3007, from pin 7 or 8 of the 3007, then thru the 47k resistors and the output of the second amp to the output socket. It's as simple as that.

[jamal]

Thank you very much for your help and for the help of the other members. Could you please just tell me the number of the output pins of the amps that I should probe? I can't figure it out from the datasheets (it says it has 2 outputs).

[jamal]

So this is what I get in the first amp input and output, and in the input of the MN3007:
www.soundcloud.com/jamal-60/working-until-mn3007-input

And this is what I get at the MN3007 output, as well as in the 47K resistors and in the final output:
https://soundcloud.com/jamal-60/mn3007-output-and-after

Does it mean that my MN3007 is busted?

[anotherjim]

You should have had sound with the 3007 bypassed. There should at least be the clean sound from the first amp (which is working) at the output (the 10k resistor then 1uF capacitor). Try to get the clean sound only with the 3007 removed and no bypass link at the 1uF output capacitor.
When you have that, put the bypass link in the 3007 socket and try to get sound at the output of the second amp. When all that works, then you can see if the 3007 fitted works.

[jamal]

I must apologize. I didn't correcly understand "HOW" to bypass de 3007, so I tried bypassing it with it  still on the board. However, upon probing the 10k resistor, only one side of the resistor had the clean sound(the side of the amp output). The other side only had that weird ticking sound. When I removed the 10k resistor from the board, I saw this underneath: http://tinypic.com/r/20p9a49/8
What is it? Will replacing the 10K resistor solve at least the problem with the clean sound not going throw?
As for the 3007, since I soldered it directly onto the board I would like to test other components first, because with everything already in it's place, removing it and soldering a new one in it's place is a bit complicated for me. I also tested the 10K resistor with my DMM and it's resistance value was ok.

[anotherjim]

Bypassing the 3007 in place should not have damaged it since the in and out pins have similar voltage....
The pic shows flux residue. It's nothing to worry about, it does tend to condense under components in a fungal attack pattern.

Use your DMM (does it have a continuity "beep" function?) to check there are no shorts circuits  between the copper strips, across the strip cuts, those bare wire links and any component legs they pass by or under.

The ticking sounds like LFO noise being picked up. Does it change with the Rate control? It might not be noticeable when everything works and it's in a box.

[jamal]

So I did the continuity test and found no shorts. After replacing the 10K resistor with a new one, I have the same results, clean sound on the amp output side and the ticking noise on the other end of the resistor. The ticking does change with the rate control, it gets faster or slower. And it's weird cause I get the same exact ticking noise on pin's 7 and 8 of the MN3007. I'm starting to think that I'm not going to make this thing work. Thanks so much for your help so far. So, what the hell is wrong with this thing?