Easy vibe

[Fede9526]

Hello everyone, I'm new in the forum and I hope I posted in the right section.
I have just built the easy vibe of John Hollis and I can not feel any effect, yet I have used the same components recommended in the original schematic.
I did some tests, adjusting the 1k trimmer, adjusting the light intensity of the LEDs that are coupled to the photo resistors, and turning the pot Depth the LEDs increase in brightness or go down until they go out, and I noticed that the LEDs turn off before the pot reaches the end of the stroke, making the pedal silent.
I think the problem is right there, since the typical vibe sound generates the LDR.
On Sabrotone, from where I took the layout, some wrote that without changing anything the pedal works very well, so I do not understand why mine should not work.
In addition, I have a question, the 2 LEDs that are outside the sheaths, which therefore do not form the LDR, should not flash? because mine remain fixed.

[ElectricDruid]

The two LEDs on the far-left are used to set a bias voltage and will remain fixed. They shouldn't be part of the opt-couplers. The other four on the bottom-right-centre are the ones that need to vary to get the effect.
I notice he specifies "low current" for the LEDs but doesn't say what that is, or what forward voltage he's expecting.

HTH,
Tom

[GibsonGM]

So, do you see the LEDs increase/decrease in brightness as the LFO ramps up and down?  If so, you should have effect.  If not, there is a problem.

- Do you have any signal at the output with the effect engaged, or is it silent, or something else? 
- Do you have the bypass switching installed, and do you get signal in bypass and not with effect engaged?
Most often, there is an error in the bypass switch wiring.

Easyvibe is....SORT of easy, but can be tricky to get going.  We will get it going eventually, do not worry Do not get frustrated, there is probably just a small error that we need to find.

Welcome to the forum!

[Fede9526]

Thanks for the answers.
The LEDs I used are red 3mm low current and the photo cells are 8k / 20k 1M, maybe those are the problem?
On the John Hollis website they recommended 10k / 20k.

When the pedal is active, the signal comes out clean but with a small variation in volume, when the pedal is deactivated the signal comes out clean.
Yes, by moving the Depth knob, the 4 LEDs increase and decrease in brightness.
I'll post the wiring I followed.

[ElectricDruid]

I don't think there's much wrong. I think it sounds like it just needs adjusting. Different LEDs will require different amounts of current, and produce different amounts of light. Similarly, different LDRs have different resistance ranges. So a circuit like this needs tuning for the parts you've used.

The "Drive" trimmer can be used to set the LED current. I'd try turning the depth up to maximum and then adjusting the "drive" to get the maximum smooth sweep you can.

There's no adjustment in this circuit for the LDRs, but it's possible to change their effective resistance by putting resistors in series with the LDR (if the on resistance is too low) or in parallel with the LDR (if the off resistance is too high).

I didn't understand the definition of the photo cells;  8k / 20k 1M? Is that 8 to 20K on resistance and 1M off resistance?

HTH,
Tom

[Fede9526]

I tried to adjust the trimmer in order to have more room to run with the pot, but the LEDs go off before the pot is at the end of the stroke.
These are the photo cells, ordered by musikding.

[ElectricDruid]

Thank you, that's clear. A photocell with a 8K-20K on resistance is going to be just the same as one with a 10K-20K on resistance. The variation between individual devices is much more than the difference between the two different types. So don't worry about that.

Maybe there is a simple problem to find then. If the drive adjustment doesn't help, there aren't many other options. Did you use the same type of LEDs for all of the six?

[Fede9526]

Yes, same LED.

[ElectricDruid]

Yes, same LED.

Good, that's important. The two LEDs + one diode on the left set the voltage at one-diode-drop higher than the forward voltage of a pair of LEDs. That's important because that becomes the point the LFO wiggles around.

[Fede9526]

The LEDs are all the same, I tried to follow the pattern as much as possible, I also used the two TL064CN.

[GibsonGM]

Too bad you don't have a scope.   Can you watch each gain section output and see if the voltage is going up and down as the LEDs light/get dimmer?  If you set it at the most slow rate you can you should be able to see this.  Just the output pins of the TL064 (don't short any other pins if you try this!  You might find a part connected just after the output pin to use as a test point....).     I am curious if your opamp is actually getting that varying signal from the LDRs.     You could just measure the voltage at the LDR too rather than near the chip; each "+" input has a cap going to it, maybe you could use that as a point to measure to see if the voltage oscillates.   The leg of the LDR NOT connected to the bias rail is what I mean...just an idea.

[Fede9526]

I did not understand what you mean, I'm not an expert, but I've already measured the IC tensions, I do not know if it can help.

IC (high)
1: 3.83      14: 3.91
2: 3.83      13: 3.93
3: 3.79      12: 0.35
4: 13.36    11: 0.00
5: 4.38      10: 3.95
6: 3.95       9: 3.57
7: 12.65     8: 0.68

IC (low)
1: 3.97      14: 4.25
2: 3.95      13: 3.95
3: 3.93      12: 3.93
4: 13.24     11: 0.00
5: 3.93       10: 3.78
6: 3.95         9: 3.79
7: 3.89         8: 3.64

I also post the photo of the side, component side.

[GibsonGM]

I was suggesting that maybe you could "see" the LFO working with the LDRs by having the rate set very low and watching your meter.

What are you powering the circuit with?  I see over 13V as power supply??

[Fede9526]

I powering with a 9v power supply.

[Slowpoke101]

Your power supply's regulation is not too good, 13.36V when it's supposed to be 9V. However don't worry about that yet.
The main concern is the voltages on the "high" IC.
Could you post a picture of the solder side of the board as well?
It would be very helpful.

[Fede9526]

I tried to power the pedal at 7.5V and the pedal works, but if I raise the pot Depth almost at the end come out of the whistles according to how the LEDs pulse.

The power supply is generic, you can select from 3V up to 12V.

[Fede9526]

Hello everyone, I understand that I have to power the pedal at 7.5V, but I have a problem.
By activating the pedal, the effect works but there is a decrease in volume, how can I fix it?

[ElectricDruid]

You could try increasing the 47K resistor on the input op-amp, the one next to the 100K. Those two set the gain, as a standard non-inverting op-amp, like this:

https://www.electronics-tutorials.ws/opamp/opamp_3.html

HTH,
Tom

[Fede9526]

To solve the drop in volume or for the whistles?
You mean the R25? From 100k could it be okay?

[Fede9526]

Is it okay to increase the resistance up to 100k or should I try first with less?