Procrastinator Trimmer Setting

[Cybercow]

I've got my Procrastinator build up and running, but there is no attack delay at any setting of the trimmer. There is output in both bypass and engaged modes. I've spent over an hour trying various trimmer settings with the Sens pot at 50% and the Attack pot set at 100% - meticulously making minute adjustments from one extreme to the other. No attack delay. Instead, I get more of a gating effect at certain trimmer settings. It's almost as if the unit is working like a gate than an attack delay. Voltages are listed below. Thoughts, suggestions and pointers are welcome.

Voltages measured with both pots set to 0%, the trimmer set at 50% and the battery supply voltage is 8.9v
IC1 Pin Voltages:

Pin 1 - 0.11	Pin 5 - 0.11
Pin 2 - 2.84	Pin 6 - 4.33
Pin 3 - 3.48	Pin 7 - 6.85
Pin 4 - 0	Pin 8 - 0

Transistor Voltages:	Collector​	Base​	Emitter​
Q1​	8.66​	2.78​	3.43​
Q2​	5.56 Drain​	2.70 Source​	5.56 Gate​
Q3​	8.64​	3.96​	6.58​
Q4​	8.61​	0​	0​
Q5​	5.31​	0​	0​
Q6​	5.31​	0​	0​

Not sure if I have a bad batch of TL071s or not. I tried 5 different TL071 opamps and they all give the same voltage readings as shown. However, when I use a TL061 in place of the TL071, the voltages changes somewhat . . . .

IC1 Pin Voltages (with the TL061):

Pin 1 - 0.08	Pin 5 - 0.08
Pin 2 - 3.91	Pin 6 - 4.33
Pin 3 - 3.48	Pin 7 - 8.41
Pin 4 - 0	Pin 8 - 0

Transistor Voltages:	Collector​	Base​	Emitter​
Q1​	8.66​	2.78​	3.43​
Q2​	5.56 Drain​	2.70 Source​	5.56 Gate​
Q3​	8.64​	3.96​	6.58​
Q4​	5.41​	2.82​	8.41​
Q5​	5.31​	0​	0​
Q6​	5.31​	0​	0​

Cybercow

 

[zgrav]

A couple of things --

1. Best results come from using a boosted signal going into the pedal with very little compression (theoretically).

2. You only get the "swell" if the gate is closed. So you need to mute the strings before playing something, and that is when you should get the swell effect. If I understand your post correctly, you are hearing a gate close when the sound is getting softer, and you do not hear any "swell" for the signal when you play a new note because the gate opens quickly. The key to getting the "swell" is to have the gate open slowly.

Take a look at the circuit diagram in your build document and follow the path from the attack pot up to Q2. Q2 is the gate. The swell effect for the pedal is created because the speed at which the gate reopens is based on how long it takes the capacitor to charge that is tied to Q2. And the speed at which the capacitor charges is based on how much signal comes through the attack pot.

Check all your connections from the part of the circuit diagram that controls the attack -- in particular make sure C3 is installed the right way and connected to the output from the attack pot, and to ground. If that does not get your pedal workings, you will need to make sure you are getting a signal starting at the sensitivity control and working your way to the attack control.

You want to make sure you are getting an audio signal going through c8 all the way through the attack control. That can be easier to check if use an audio probe so you can follow your signal through the different parts of the pedal (do a google search on how to make a simple audio probe).

 

[Cybercow]

zgrav - thank you for that. It will help me get a better understanding of how to specifically signal trace this circuit. Understanding how some of these circuits is like trying to grasp engine timing sequences for the first time. I already have an audio probe and use it judiciously. With the info you've provided, I should be able to better suss it out. Thanks again.

Cybercow

 

[!obey]

i just finished building mine and wanted to throw in my two cents and qualitative/anecdotal analysis. the trimmer setting was important to getting a balanced response across all strings. without adjusting the trimmer, it seemed as though i could get good gate/swell on unwound strings and the wound ones would be below the threshold (assuming i was picking consistently). this wasn't fine-tuneable enough using just the pot. after adjusting the trimmer, i could get a *much* more uniform thresholding across all strings. also, this seemed to be independent of where on the neck i was fretting, although there is still a more pronounced response difference between wound/unwound strings as the sensitivity pot is turned toward extremities.