Tri-vibe pedal by aion-Fx makes womping noise

[TTANGO]

This is my second post, as my first had to do with toasting a resister, so there are still issues.
The resister has been replaced and works.

Now this pedal used to work. other than slight popping noise when I switched modes, and I discovered a wrong IC
All IC's are correct and in the correct direction.  The led has never blinked. The LED does not show up on the pedal board image, but is between R26 and R29.

Now, I replaced IC 2 because there was a lot of noise and I had missed some soldering R2 R33 R30 because I was sloppy.  Cleaning the board with alcohol really helps see your work, huh LOL

Now the pedal is making a womp womp womp sound that speeds up and slows down with the rate, and depth effects.  There is no difference when I switch modes.  Also, the pedal makes this sound if the guitar is plugged in or not.

The other day we replaced IC 4 and it made no difference.  (I had a spare)
Thanks
schematic
https://aionfx.com/app/files/docs/tri-vibe_documentation.pdf

[Kevin Mitchell]

Confirm values of R19(100K) and R20(47K). These limit the amount of resonance. If these were too low or a direct short it would cause self-oscillation.

For the LED, are you sure you've soldered it the correct way?

[Radical CJ]

It sounds like you have added a rate indicator LED that is not in the schematic. Is that what you mean by an LED between r26 and r29?

Can you show how you have done this? It is possible to add a rate indicator to the LFO but if you've done it wrong it could create noises.

[TTANGO]

I will verify the resistors
As to the Led, the space on the board is there for one, it just isn't on the diagram in the documentation. On the schema it is D4. bottom right.  I have gotten it to light up by putting a huntron tracker on one of the resistors below it, but I don't remember which one, but I can try that again and will post.

[Aph]

I think D4 is part of the LFO shaping circuit around IC2B. It's not a visual display of the LFO rate.

[Radical CJ]

I think D4 is part of the LFO shaping circuit around IC2B. It's not a visual display of the LFO rate.

I don't have the schematic in front of me, but if the led in question is D4 then I believe you are correct, and it is perhaps affecting the slope of the wave. In which case, probably not the culprit.

Just to confirm, does the pedal vibe the guitar signal when on? Or does clean signal pass through with the womp, or no sound but womp?

[TTANGO]

When bypassed I get no sound from the pedal other than guitar.  When on, I get the self oscillation.

I checked the two resistors and they are correct, but I will replace them as a test.  Will Post later

This pedal used to work, but I smoked a resistor.  a little back story
I had toasted the R37 resistor when out of the box testing to debug the popping from the mode switch.  After I replaced the resistor it was really noisy, just grabbing wires caused noise and that is when I discovered I had a TL022 in IC2 where it should have been a TL062. I replaced the IC2 and the noise went away, and then the self oscillating started.  We scoped and got to IC4, and my friend was suspicious of it, and so I replaced that, with no changes. 

[aion]

This pedal used to work, but I smoked a resistor.  a little back story
I had toasted the R37 resistor when out of the box testing to debug the popping from the mode switch.  After I replaced the resistor it was really noisy, just grabbing wires caused noise and that is when I discovered I had a TL022 in IC2 where it should have been a TL062. I replaced the IC2 and the noise went away, and then the self oscillating started.  We scoped and got to IC4, and my friend was suspicious of it, and so I replaced that, with no changes.

Unfortunately if you toasted R37 it may mean that there are other significant issues with the power supply, and anything downstream could be affected. I would start by replacing C11, the main filter capacitor, and perhaps even increasing it to 220uf. Might as well replace IC1 as well since it's the only one that hasn't been swapped.

You might also try increasing R37 to 47R just to help prevent that from happening again. 22R is a little on the low side for this much current draw, and while I haven't heard of any other reports of failure in the past few years, it doesn't surprise me that it would be the first thing to buckle under adverse circumstances.

[TTANGO]

This pedal used to work, but I smoked a resistor.  a little back story
I had toasted the R37 resistor when out of the box testing to debug the popping from the mode switch.  After I replaced the resistor it was really noisy, just grabbing wires caused noise and that is when I discovered I had a TL022 in IC2 where it should have been a TL062. I replaced the IC2 and the noise went away, and then the self oscillating started.  We scoped and got to IC4, and my friend was suspicious of it, and so I replaced that, with no changes.

Unfortunately if you toasted R37 it may mean that there are other significant issues with the power supply, and anything downstream could be affected. I would start by replacing C11, the main filter capacitor, and perhaps even increasing it to 220uf. Might as well replace IC1 as well since it's the only one that hasn't been swapped.

You might also try increasing R37 to 47R just to help prevent that from happening again. 22R is a little on the low side for this much current draw, and while I haven't heard of any other reports of failure in the past few years, it doesn't surprise me that it would be the first thing to buckle under adverse circumstances.

Ok, will do.  R20 and R19 didn't make any difference

[TTANGO]

This pedal used to work, but I smoked a resistor.  a little back story
I had toasted the R37 resistor when out of the box testing to debug the popping from the mode switch.  After I replaced the resistor it was really noisy, just grabbing wires caused noise and that is when I discovered I had a TL022 in IC2 where it should have been a TL062. I replaced the IC2 and the noise went away, and then the self oscillating started.  We scoped and got to IC4, and my friend was suspicious of it, and so I replaced that, with no changes.

Unfortunately if you toasted R37 it may mean that there are other significant issues with the power supply, and anything downstream could be affected. I would start by replacing C11, the main filter capacitor, and perhaps even increasing it to 220uf. Might as well replace IC1 as well since it's the only one that hasn't been swapped.

You might also try increasing R37 to 47R just to help prevent that from happening again. 22R is a little on the low side for this much current draw, and while I haven't heard of any other reports of failure in the past few years, it doesn't surprise me that it would be the first thing to buckle under adverse circumstances.

Ok, will do.  R20 and R19 didn't make any difference

I had already increased  R37.
I had just replaced IC1 just before I saw your post.
I replaced C11 with a 220uf and no change.  still self oscillating.  Boy did I bugger this one.

[antonis]

I'd delete C13..
(or place a low value, 50R to 100R say, series resistor between IC2A output and C13..)

[TTANGO]

Ok, I am getting somewhere

The oscillation is impacted by the depth knob.  If I turn down the depth knob it goes away, and I can adjust rate and It will work.  As I turn up the depth knob the self oscillation starts.  The rate knob will speed it up, but does not seem to have any impact on starting the oscillation if that makes sense.

I think that we are getting somewhere.

[Kevin Mitchell]

Ok, I am getting somewhere

The oscillation is impacted by the depth knob.  If I turn down the depth knob it goes away, and I can adjust rate and It will work.  As I turn up the depth knob the self oscillation starts.  The rate knob will speed it up, but does not seem to have any impact on starting the oscillation if that makes sense.

I think that we are getting somewhere.

I was going to suggest what I would do, but I realize we don't have voltages for much of the circuit
Voltages for each IC pin would be nice, but I'm mostly curious to what you see on the pins of the LM13700.

I was going to suggest raising the value of R10 and R17 from 10k to next best (12k, 15k, 18k and so on, whatever you have).
But I realize that if the pedal is behaving in an unusual manner, perhaps there's something wrong with VB which is suppose to half of VA. Pin voltages of the OTA will verify.

[TTANGO]

Ok, I am getting somewhere

The oscillation is impacted by the depth knob.  If I turn down the depth knob it goes away, and I can adjust rate and It will work.  As I turn up the depth knob the self oscillation starts.  The rate knob will speed it up, but does not seem to have any impact on starting the oscillation if that makes sense.

I think that we are getting somewhere.

I was going to suggest what I would do, but I realize we don't have voltages for much of the circuit
Voltages for each IC pin would be nice, but I'm mostly curious to what you see on the pins of the LM13700.

I was going to suggest raising the value of R10 and R17 from 10k to next best (12k, 15k, 18k and so on, whatever you have).
But I realize that if the pedal is behaving in an unusual manner, perhaps there's something wrong with VB which is suppose to half of VA. Pin voltages of the OTA will verify.

1. 1.45        16.  1.45
2. 5.48.       15.  5.48
3. 4.81.       14.  4.81
4. 4.81.       13.  4.81
5. 6.04.       12.  5.8
6. .2 mv.     11.  9.02
7. 6.03.       10. 5.80
8. 4.85.        9.  4.61

[Kevin Mitchell]

Thanks!
VB is looking a little high by a few hundred millivolts. What do you see on pins 1 & pin 3 of the TL062? If they're not identical then try swapping the TL062 with any other dual opamp.

[TTANGO]

Thanks!
VB is looking a little high by a few hundred millivolts. What do you see on pins 1 & pin 3 of the TL062? If they're not identical then try swapping the TL062 with any other dual opamp.

Pin 1 and 3 are not identical. 1 4.59. 3.  4.47. pin 3 takes a while to settle
I swapped for another tl062 and get the same results.  Pin 3 takes a few seconds to settle down

sorry made a correction to pin 3 value. 4.47 not 4.7

[Kevin Mitchell]

The voltages on the pos. inputs of the OTA should not be higher than VB. In fact they should be slightly lower considering the resistors between them. Idk. Maybe I'm missing something.

You can try my previous suggestion on swapping R10 and R17. This will further limit the effect the depth has on the filter. You'll want a value that allows the depth fully clockwise to be usable - which is why I suggested incremented values.

[TTANGO]

The voltages on the pos. inputs of the OTA should not be higher than VB. In fact they should be slightly lower considering the resistors between them. Idk. Maybe I'm missing something.

You can try my previous suggestion on swapping R10 and R17. This will further limit the effect the depth has on the filter. You'll want a value that allows the depth fully clockwise to be usable - which is why I suggested incremented values.

does changing the C11 from 100uf to 220muf have any impact, because I did that.

[TTANGO]

well, I replaced R10 and R17 with 12k and it made a popping noise and doesn't work except in Bypass mode.

I'm done.

Ill review this some time later, but thanks everyone