The Quackmire: A simpler vactrol LP envelope filter for 1590A

[sevrien]

Update,

found a fault in the power supply, corrected in this version

Is someone able to verify this layout on sight?
I know I drew it myself, but, its not working and I don't seem to track down the problem.
I do get a very quiet signal but it sounds distorted and not quacky at all.

I'm using a 2N5088 for Q1,
the LED between pin 3 and 4 of the IC lights up bright, the other faintly and does not flicker when playing.

I assumed there was a short circuit somewhere but I can't find one.

Thanks in advance

[sevrien]

Nevermind previous post,


here's a working layout.
Had some serious buzz from the range pot, after grounding the housing it was gone.
Still some 50hz hum in the circuit, not sure where it comes from.

[jfrabat]

Anyone made the schematic with the switch?  If not, I can make it, but just wanted to save myself some work...

[Fancy Lime]

Anyone made the schematic with the switch?  If not, I can make it, but just wanted to save myself some work...

Here you go:
https://postimg.cc/GBM8dF1w

Cheers,
Andy

[jfrabat]

Started building one of these for my son's base guitar   First time using veroboard for me, and it has been an experience...  Anyway, got the board done, but still need to attach all the off board components (pots, switch, jacks, stomp switch, LED, and caps for switch).  Hopefully, I did not screw up my soldering and the thing will work!

[jfrabat]

Hey, guys.  Need some help here...  Got bored during the quarantine, and decided to have a go at this one (had it pending for my son for some time!).  Anyway, I used what I had on hand, so some components are a bit oversized!   

Anyway, I wired it all up (outside of the box) and I am getting no sound.  Now, my intention was to give you some voltages, but, unfortunately, my MM died on me, and Amazon has yet to ship the new one!  Not to mention for another week or two to get to Panama, and then maybe see if the forwarder is still delivering goods (by law, we cannot leave the house save for 3 hours a day, 2 days a week!).

Anyway, I thought I would compensate that with lots of pics.  Please bear in mind that I am dyslexic, so it is very possible I have switched something other than what I caught during my checks.

I used this as the base:


Overview


This is one correction I had to make, and I was out of holes, so I soldered to the cap leg...






Not exactly ideal size for a pedal, but it what I had...


https://i.postimg.cc/dtvyzgCH/20200413_155139.jpg

Now, the switch I had to go from the schematic; did I get this right?






And, of course, the ugly side of things...


So, do you see anything out of place or a wrong value?+

[Fancy Lime]

The only thing I see, is that you have installed C11 (1u) twice, once on the board and once at the switch. It is only supposed to be on the board. Only C10 and C12 are supposed t bet on the switch. However, that cannot be the reason for no sound at all. When you say "no sound", do you mean none at all or is there at least noise or something? You can try touching the terminals of the components with a wire or nail or whatever (anything that is conductive and connected to you hand) while the circuit is connected to an amplifier (which is set not too loud). Start from the very end and work your way backward. When touching a trace, there should be a loud BZZZZZZ. As you work your way back from the output along the signal path, at what point does that noise disappear? It's the poor mans audio probe! If you have an audio probe, you can use that as well, of course.

The problem I always have with strip board, is that it is pretty difficult to diagnose problems. There are often shorts or cold connections that are difficult to see but looking at all the solder work with a magnifying glass is usually my first step.

Hope that helps a bit,
Andy

[cab42]

The first thing I always do, when something on vero doesn't work, is to run a stanley knife between the copper traces. Those solder bridges can be almost invisible. That has solved a fair number of problems with non-working builds.

There's a couple of places on the photo of the copper side that looks suspicious.

[jfrabat]

Before the MM died, I did a connectivity test, so there are no unwanted bridges in the soldering (at least none that I detected at that time).  I will go through it with an scratch owl and make sure, but I do not think that is the issue...  I will try the audio probe and see what that turns up.

[jfrabat]

My new MM arrived today!!! YAY!!!

SO, I started checking for bridges (did find two; not really bridges in the solder sense, but actually, when I drilled the breaks, I left a tiny little sliver of copper in 2 places that were providing continuity where there should not have been).  Then I found two wiring errors: 

1. A jumper was going to the wrong line of the board
2. The output was soldered at line 13 instead of 14 (I believe the is a possibility that this could cause no sound to come out of the output; but I will blame this on the design, as this type of error shoul dhave been foreseen and allowed for!).

Connected the bass again, but no sound still!  I really thought I had the problem found when I found the above, but, the problem persists...  So, here are a few voltages for your guys:

Input Voltage: 9.52V
Input after D2: 9.27V

Q1:
C: 8.90V
B: 4.99V
E: 4.48V

IC1:
1: 1.319V
2: 1.599V
3: 1.141V
4: 0V
5: 2~2.4V
6: 3~3.3V
7: 2.5~2.8V
8: 8.9V

Anything else I should measure?

[Fancy Lime]

Looks like there is something wrong between the emitter of Q1 and pin 5 of the IC. These should be much closer together. Can you take the voltages at all the junctions in between? So after R6, after the range pot, after R7. Does any of this change when the range pot is at maximum vs range at minimum?

Also: With no input signal, the voltage should not vary on pins 5, 6 and 7.

One possible explanation is that the filter opamp half (input at pin 5) sucks too much current. Opamps are somewhat variable and what worked with my NE5532 may not work as well with yours. Although the way the circuit is designed, this should lead to a little unwanted distortion at worst but not to no signal.

At the moment my money is on a bad connection between E of Q1 and pin 5.

Oh and I also just now realized that the Sensitivity pot is connected wrong in both the schematic and the layout. Lug 2 should be tied together with lug 3 instead of with 1. That will only change the direction and characteristic of the Sens control, though.

Hope that helps. Let me know how it goes,
Andy

[jfrabat]

EDIT: deleting post (duplicated)

[jfrabat]

Looks like there is something wrong between the emitter of Q1 and pin 5 of the IC. These should be much closer together. Can you take the voltages at all the junctions in between? So after R6, after the range pot, after R7. Does any of this change when the range pot is at maximum vs range at minimum?

Let me re-measure, just to be sure on the readings.  The great advantage of home office is that the pedal is IN the office today!  At least ONE good thing from this Pandemic!  Here are today's readings (making sure not to touch the board and introduce static into the system!):

Input Voltage: 9.52V
Input after D2: 9.26V

Q1:
C: 8.90V
B: 4.99V
E: 4.48V

R6:
From Q1e: 4.48V
To Range pot: 3.84V

Range Pot
Pin 1+2: 3.83V
Pin 3: 3.33~3.84V (depending on pot position)

R7:
From Range pot: 3.33~3.83V (depending on Range pot position)
To R8: 3.32~3.82V (depending on Range pot position)

R8:
From R7: 3.32~3.82V (depending on Range pot position)
To IC1 5: 3.30~3.80V (depending on Range pot position)

IC1:
1: 1.304~1.311V (depending on Sensitivity pot and making sure not to touch the board; voltage is stable)
2: 1.311~1.599V (depending on Sensitivity pot and making sure not to touch the board; voltage is stable)
3: 0.867~1.150V (depending on Sensitivity pot and making sure not to touch the board; voltage is stable)
4: 0V
5: 3.30~3.79V (depending on Range pot and making sure not to touch the board; voltage is stable)
6: 3.94~4.19V (depending on Range pot and making sure not to touch the board; voltage is stable)
7: 3.94~4.19V (depending on Range pot and making sure not to touch the board; voltage is stable)
8: 8.9V

Mind you, as soon as I introduce some static to the system, voltages start oscillating, which I guess is normal, as it is detecting a signal, right?

Also: With no input signal, the voltage should not vary on pins 5, 6 and 7.

Yes and no...  I was holding the board in my hand, so it could have been getting some static from me.

Oh and I also just now realized that the Sensitivity pot is connected wrong in both the schematic and the layout. Lug 2 should be tied together with lug 3 instead of with 1. That will only change the direction and characteristic of the Sens control, though.

I will fix that once I get this working.  Thanks for the heads up!

[Fancy Lime]

Hmmm, those voltages look OK now. So the DC path seems not to be the problem. So let's try to hunt down the problem together.

Do you have alligator (crocodile) clip wires? Those would make this easier but you can also solder temporarily or figure out some other way of making a temporary connection with the gear you have.

1. Try to attach a 4.7k resistor and a red LED in series from the middle pin of the mode switch to ground. If you play something into the input with the sensitivity pot turned half way up, does the LED light up?

If yes, then the problem likely lies in the filter section or the vactrol. If no, it lies in the envelope detector or the input stage.

2. If the LED does light up in the first test: Try to add a parallel 1k to 10k resistor to the resistor side ends of the vactrol (the two wires that meet the two ends of R6) with alligator wires from the vactrol wires. If you play something, do you get output.

3. Check the orientation of the vactrol. Where is the dot? The dot marks the cathode (minus) of the LED side.

4. If the LED in test one does not light up, run an alligator wire from E of Q1 directly to the lowermost leftmost pad on the board (15th row, 1st column).  If you play something into the input, do you get signal at the output? Is the trimpot turned up?

Those are the things I can think of right now. I'll let you know if something else pops into my mind.

Cheers and good luck,
Andy

[bluebunny]

Here's mine that I finally boxed up yesterday.



It's pretty cool.    Thanks Andy!  If anyone is interested in my vero layout, here it is:



Watch out for some of the cuts which aren't too obvious: three underneath the 10K in the bottom left, and two under the 33K to its right (I think the rest are reasonably clear).  Watch out also for the two slightly kinked wire links.  The vero was a scrap piece left over from something else which explains why it's the shape it is, and why some of the controls aren't attached at the edges!  BTW, I added the "less peaky" mod ("Q" switch on mine).  And I adjusted my volume trimmer to be full blast. 

(Edited to fix image links.)

[Kipper4]

Great graphics Marc. Nice work.

[Fancy Lime]

Most excellent, Marc! Nice build and way groovy graphics! Thanks for posting the layout!

Groove is in the heart!
Andy

[ljudsystem]

  Great work! love the Bootsy graphics!

[Elijah-Baley]

Thanks for sharing.

[jfrabat]

Hmmm, those voltages look OK now. So the DC path seems not to be the problem. So let's try to hunt down the problem together.

Do you have alligator (crocodile) clip wires? Those would make this easier but you can also solder temporarily or figure out some other way of making a temporary connection with the gear you have.

1. Try to attach a 4.7k resistor and a red LED in series from the middle pin of the mode switch to ground. If you play something into the input with the sensitivity pot turned half way up, does the LED light up?

If yes, then the problem likely lies in the filter section or the vactrol. If no, it lies in the envelope detector or the input stage.

Like this?



If so, the LED DOES light up (not too brightly, but it does light up enough to be clearly seen in daylight in a lighted room).

2. If the LED does light up in the first test: Try to add a parallel 1k to 10k resistor to the resistor side ends of the vactrol (the two wires that meet the two ends of R6) with alligator wires from the vactrol wires. If you play something, do you get output.

No, I do not (used 10K).

3. Check the orientation of the vactrol. Where is the dot? The dot marks the cathode (minus) of the LED side.

Vactrol is correctly oriented (checked).

4. If the LED in test one does not light up, run an alligator wire from E of Q1 directly to the lowermost leftmost pad on the board (15th row, 1st column).  If you play something into the input, do you get signal at the output? Is the trimpot turned up?

Those are the things I can think of right now. I'll let you know if something else pops into my mind.

Cheers and good luck,
Andy

What do I try next?  I am stumped...