Naughty Fish Help

[Mycyk]

Newbe here.... This is my second build

I have a partially working unit. It does 'yeow' (or down) but does not 'wha' (or up) and the peak pot has no effect. I assume that if the effect partially works, the Hi/Lo & LP/BP/HP switches work and the gain & volume pots work that the wiring is OK. The Peak pot itself appears to work based on measuring it in the circuit.

I have done the following:
Checked are rechecked components and values - OK
Reflowed the solder

Following are voltages measured with the effect bypassed and input V=11.7:
   1   2   3   4   5   6   7   8
IC 1   3.3   3.3   1.5   0.7   5.2   6.2   2   11.2
IC 2   2.1   1.7   1.6   0.7   4.5   4.2   8.6   11.2
IC 3   10.2   0   0   0.7   0   4.8   10.4   11.2
IC 4   1.4   6.1   0   -4.8   -10.6   2.5   3.7   11.2
                        
   Inputs      Outputs               
VACT 1   8.6   6.8   0   2            
VACT 2   8.6   6.8   4.9   10.2            

I am concerned about the output of VACT 1 being so low. Could it be bad or could it be a problem in the circuit after it?
Any other suggestions/ideas welcome.
Thanks.....

[mgwhit]

Based on the 11V you're putting into this circuit and the -10.6V you're reading on IC4:pin5, I don't understand why you're getting ~0V on pin 4 of IC1, IC2 and IC3.  Those should all be  at or around -10.6V.  There might be an issue with VACT1, but I'd concentrate on that missing negative voltage on your op amp ICs first.  Good luck!

[RobA]

I just happen to have my Naughty Fish sitting open right now as I've just screwed up putting a decal on it, but that does make it easy for me to take some voltages. Mine's the 2014 version. I don't think that'll make a difference.

Pots are both at 12:00. Toggles are set to LP, Down, Hi

The input voltage is at 9.25V

IC1:   
   1   0V
   2   0V
   3   0V
   4   -8.23V
   5   0V
   6   0V
   7   0V
   8   8.66V
IC2:    
   1   ~80mV drifting
   2   22mV
   3   22mV
   4   -8.25V
   5   3.44V
   6   2.57V
   7   6.48V
   8   8.66V

IC3:
   1   0V
   2   0V
   3   0V
   4   -8.25V
   5   0V
   6   0V
   7   0V
   8   8.66V

IC4:
   1   1.37V   
   2   4.62V
   3   0V
   4   -3.88V
   5   -8.24V
   6   2.55V
   7   1.41V
   8   8.66V

Vactrol 1:
   1   6.48V
   2   4.93V
   Resistor side both pins at 0V

Vactrol 2:
   1   6.48V
   2   4.93V
   Resistor side both pins at 0V

If a voltage read less than 1mV, I put it at zero.

[mgwhit]

Mycyk, take a look at Rob's IC1 and IC3 voltages as well as pin4 on IC2.  Those are the places where it is the most glaringly obvious that something is horribly wrong with your negative power rail.  What's strange is that you have correct negative voltage on IC4:pin5, but not on any of your op amp ICs.  From the schematic that looks totally impossible -- there are direct connections from IC4:pin5 to the negative voltage supplies on IC1-3.

I think there are three possibilities (in order of probability):

1. Cold solder joint on IC4:pin5
2. Broken trace (especially the pad at C14)
3. Cold joints on IC1-3:pin4

Can you confirm whether or not you have approximately -10.6V on the negative lead of C14?  Decent photos of both sides of your board would help tremendously, too.

[Mycyk]

Thanks for your replies. I feel like a dope - obviously supply voltages should be the same for all the IC's.  Let me try again - I have remeasured them and they are similar to RobA's:

IC 1   
1 0
2 0
3 0
4 -10.5
5 0
6 0
7 0
8 11.0

IC 2
1 3.5
2 0
3 0
4 -10.5
5 4.4
6 4.4
7 4.5
8 11.0

IC 3
1 0
2 0
3 0
4 -10.5
5 0
6 0
7 0
8 11.0

IC 4   
1 1.4
2 6.0
3 0
4 -4.8
5 -10.6
6 2.5
7 1.4
8 11.0
                        
           Inputs   Outputs               
VACT 1   4.4   2.7   0   0            
VACT 2   4.6   2.8   0   0   

I had to substitute C1 and C9 with tantalum, and C4 is a large cross-over cap so I had to lay it down to fit it in the box. I replaced C13 because I thought it was bad but I still have the same issues. Pictures attached.

The pedal works as expected with the Range switch 'Down' but not with it 'Up'. The voltage to the Vactrols appears to be too high because the LED is lit even with the gain control at minimum, but I can't read the schematic well enough to figure out why........

I made an audio probe and listened to many different points tonight but nothing really makes sense to me. Anything on IC 2 sounds very distorted, but inputs and outputs from the board are fine.

Thanks again!

[Mycyk]

Confirming that I do have -10.4 V at -ve pin on C14.

[mgwhit]

Thanks for correcting those voltages and posting the photos.  All of the resistors down in the "Range" potion of the circuit look fine.

I'm having trouble reading your R6, though.  Is that a five- or four-band color code?  If it's four-band, I would expect orange - white - yellow - gold.  If it's five-band I would expect orange - white - black - orange - (brown?).  To me it looks like orange - white - brown - gold (390R).  Apologies if I'm just misreading that.

[Mycyk]

Yes you're absolutely right. Even though I checked it twice (I saw what I wanted to see!) R6 is 390R not 390K. Will swap them and let you know what happens.

Thanks!

[mgwhit]

Cool.  I hope that's it.  That was certainly what was making the Peak control unresponsive.  The 390K resistor is in parallel with the 250K pot to bring the maximum value down to about 150K, which is what's in the original Mutron III.  A 390R in the same position brings the maximum setting to, well, about 389R.

I'm not sure why that would affect the Range functionality, though.  I wonder if we'll find something else after you've fixed that.  Fingers crossed, though!

[Mycyk]

Thanks mgwhit!
Changing the resistor did fix the sweep and peak controls. They both work really well now.

Still have the issue with only the 'Down' switch working. The 'Up' is a little better but still has too much voltage so it's basically almost full open even with the Gain pot at minimum.

I tried a regulated power supply at 9 volts and it is about the same, but the 'Down' does not work as well. The range of sweep and the sensitivity are limited. The indicator LED does not come on at all in the 'Down' position but is still on all the time in the 'Up' position.

Input is now V=8.96:
(omitted all zeros to make the list shorter)
IC 1   
4 -7.8
8 8.4

IC 2
1 1.7
4 -7.8
5 2.9
6 2.8
7 4.4
8 8.4

IC 3
4 -7.8
8 8.4

IC 4   
1 1.4
2 4.6
4 -3.6
5 -7.8
6 2.5
7 1.4
8 8.4

With the range switch in the up position only IC 2 changes to these:
IC 2
1 4
4 -7.8
5 3.3
6 3.4
7 2.5
8 8.4

I'm looking into the supply for IC 2 and checking my values and soldering again.

Looking forward to any other suggestions the group might have.
Thanks again!

[mgwhit]

Cool.  Glad you're making progress!  Can you post the voltages at the anode and cathode of your LEDs (LED1, VACT_1A, VACT_2A) with the Range switch in the Up and Down positions? 

[Mycyk]

Here are 2 sets of measured voltages with no input to the pedal. The first is with the 11V supply:
Range switch Down
Vactrol 1
Anode 5.1
Cathode 3.3

Vactrol 2
Anode 5.1
Cathode 3.4

LED
Anode 1.71
Cathode 0

With Range switch Up
Vactrol 1
Anode 4.1
Cathode 2.3

Vactrol 2
Anode 4.1
Cathode 2.3

LED
Anode 1.65
Cathode 0

Using my regulated 9 V supply:
Range switch Down
Vactrol 1
Anode 2.8
Cathode 1.0

Vactrol 2
Anode 2.8
Cathode 1.0

LED
Anode 1.38
Cathode 0

With Range switch Up
Vactrol 1
Anode 4.2
Cathode 2.4

Vactrol 2
Anode 4.2
Cathode 2.4

LED
Anode 1.67
Cathode 0

All of these change a lot with music from my MP3 player into the pedal.  Vactrol anode voltages swing between -5 to +5 with the Range switch Down but are pegged at 6.4 with the Range switch Up.

Thanks for any further assistance or ideas.

[mgwhit]

Thanks!  I've gotta admit that I'm in over my head here.  I'm going to throw out some ideas and maybe someone with more experience with this circuit can chip in.  I 'd like you to try two more things:

1. In both Up and Down positions of the Range switch, check to see if the voltage on the cathode of D2 wiggles when you play music through the effect.  It should move up and down in both switch positions.  If it does in the down position and doesn't in the up position then we know the problem is in the rectifier (IC2_A).  If it moves in both positions, we can assume that the problem is in the inverting amplifier of IC2_B. 

2. With the power off, do a thorough continuity test of all of the lugs on your Range switch.  Test to confirm that the correct lugs are connected in each switch position and that the incorrect lugs are not connected.  (If you don't know how to do this, let us know.)  Confirm that none of the lugs has any continuity to ground in either switch position.

Thanks for keeping up with this thread.  Every time you post more information here, you get closer to finding the problem...even if it feels like it's taking forever.  Good luck!

[Mycyk]

Okay, # 2 first: I measured the range switch in situ with my ohmmeter and it appears to be working properly. There is no direct connection to ground and the pins show the correct connections when switched.

Cathode of D2 shows voltage sweeps in both switch positions. I also swapped the IC TL072s and D2 shows the same for all 3 different IC TL072s  in all 3 IC sockets. Also pin 7 of all 3 ICs show voltage swings at all times whereas pins 5 & 6 only show voltage swings with the Range switch in the Up position. Based on this data it appears to me that all 3 IC TL072s are working, at least all 3 are the same.

With the Range switch in the Up position I am now able to hear some 'wahing' with full range signal but it is very slight and only in the upper treble range (above about 2K Hz, which is why I couldn't hear it previously when testing with my bass). With the Range switch in the Down position the effect is very noticeable and can be adjusted from low through higher frequencies with the mode and Hi/Lo switch, which I consider normal. If this was the effect I wanted I would stop here and box it up but the Up effect (basically an autowah for my bass) is what I'm really looking for.

Any ideas on how I can get the effect down to lower frequencies with the Range switch in the Up position? Based on observation of the LED the voltage appears too high because it never goes off. Is there a mod to the circuit which would affect this?

Thanks again for all your help. I have been working on this build on and off since November so any progress is good at this point.......

[mgwhit]

I've gotta admit, I'm stumped, but this would be as good a time as any to triple check the values of all of your capacitors.  C4 controls the frequencies that drive the envelope, so that's a great place to start.  Not sure why it would only affect the Up position, though, especially since your R12 and R13 values look good.