3PDT Popping (Vero Project)

[Ginsly]

I have some pcbs to tackle, but wanted to put this Vero project together to shake the dust off. It's related to the Mini-Bone, but has a couple odd differences that piqued my interest. Just wanted to mess around with something small and work on my soldering. I used this layout:

I used one of those Utility 3PDT pcbs that has LED, CLR, etc etc, and actually found that using an LED affected the Starve (Bender Knob) function in a way that wasn't great - plus, it dimmed the LED! I left the CLR on the 3PDT board, but pulled the LED. (It looks like there's an LED installed in the pic, but those are just sockets.)

It does work well, thankfully - sounds wonderfully broken on many settings, especially since I ridiculously used a C1K for the Starve pot... This thing can survive on surprisingly low power!

Problem is, it pops when I turn it on and off - I (luckily) haven't experienced this issue much if ever, and I have the feeling it's due to the simplistic Vero setup (no electro or diode in power section), but I figured maybe it could be the missing LED... Maybe I need to jumper those pads..?

The back of the enclosure is covered in electrical tape, so nothing should be shorting against it - plus, it happens whether or not the back is attached.

I'd love to know how best to troubleshoot this, given that it's not a straightforward pcb project... Do I add an electro somewhere? 1M resistor? Here's a pic, although it's probably not too helpful... or too pretty!

 

[gonzo]

You could try a 1M resistor to ground at the input and output. Alligator clip them in and test it.

 

[Ginsly]

You could try a 1M resistor to ground at the input and output. Alligator clip them in and test it.

Thanks @gonzo! This is something I've seen people mention - usually at the input, but I'll certainly try both. In a "finished" situation like this, what is the easiest way to incorporate a 1M resistor at the Input and Output? Maybe the jacks themselves? On the 3PDT?

There's a perf layout for this that also incorporates a 100uf electro across +/-, but I'm unsure of where that would go (and if it would make any difference). Same thing for using a jumper on the LED pads - I'm not sure what that would achieve.

It's strange - I'm also getting some serious low-frequency oscillation at many points on the Attack and Starve knobs where I didn't when I breadboarded it! Used nearly all of the same components, too. Bosstones can do this at the lower end of the Attack knob, but this one is doing it mostly at higher Fuzz settings. I mean, this thing IS a mangled Bosstone and all, but it's odd that this didn't happen when testing... hmm

 

[Robert]

It's worth a shot but you already have a 100K potentiometer to ground on the input and output that is acting as a pulldown resistor (much lower than 1M).

The wire runs and vero layout could be contributing to the oscillation.


Do you have an LED installed?

If so, disconnect it (or remove the current limiting resistor from the 3PDT breakout) and see if that helps.

If not, don't worry about jumping the LED pads, that would just make the problem worse by increasing inrush current.


EDIT: Nevermind, I see you've pulled the LED already. A little bit of reading goes a long way.

 

[Ginsly]

It's worth a shot but you already have a 100K potentiometer to ground on the input and output that is acting as a pulldown resistor (much lower than 1M).

Huh, I did NOT realize things worked that way - very interesting. I guess it wouldn't really hurt to try, but I'm not sure exactly where the best place to put them would be in this particular situation. Failing that, I'm not sure how to diagnose/cure the switch pop.

The wire runs and vero layout could be contributing to the oscillation.

Yeah.... those wires are way too long - I just kinda overestimated and never trimmed em down! The thing is, the breadboard test leads were WAY longer, and I didn't get any of the motorboating/low osc that I am now. This is very much "just some dude's" layout from 15 years ago, and I need to remember that. Most Bosstones I've used over the years have had this, but never to this degree and never on high-gain settings.

Do you have an LED installed?

If so, disconnect it (or remove the current limiting resistor from the 3PDT breakout) and see if that helps.

I had an LED/CLR installed on that 3PDT board, but it totally killed the low-voltage low-octave sounds. I guess I never realized how much power LEDs can use. There's no LED installed at the moment, and it sounds like I shouldn't jumper the pads. I was wondering if I should remove the CLR since it's unnecessary, and it sounds like that might be a good idea.

Thanks Robert! I have some excellent PPCB boards I don't wanna screw up, so figured I'd go back to Vero for a sec. I can see why people prefer pcbs...

 

[Robert]

I had an LED/CLR installed on that 3PDT board, but it totally killed the low-voltage low-octave sounds. I guess I never realized how much power LEDs can use. There's no LED installed at the moment, and it sounds like I shouldn't jumper the pads. I was wondering if I should remove the CLR since it's unnecessary, and it sounds like that might be a good idea.

Was your LED being powered by the starve control? (Did the starve control affect the brightness of the LED?)

Having an LED shouldn't affect the tone of the circuit unless maybe it was connected to lug 2 of the "Bender" pot. Moving that connection over to lug 3 should prevent any sort of interaction. If the LED is removed (and it's pads aren't jumpered) the CLR is electrically out of circuit so leaving it in place won't have any impact.

I'd check for leaky input / output coupling capacitors (C1/ C5) and try routing the wires in different ways. Maybe there is some parasitic oscillation outside of the audible range that is contributing to the popping.

 

[Ginsly]

Was your LED being powered by the starve control? (Did the starve control affect the brightness of the LED?)

Having an LED shouldn't affect the tone of the circuit unless maybe it was connected to lug 2 of the "Bender" pot. Moving that connection over to lug 3 should prevent any sort of interaction. If the LED is removed (and it's pads aren't jumpered) the CLR is electrically out of circuit so leaving it in place won't have any impact.

I'd check for leaky input / output coupling capacitors (C1/ C5) and try routing the wires in different ways. Maybe there is some parasitic oscillation outside of the audible range that is contributing to the popping.

First off - the pop seems to be gone! Problem is, I'm not exactly sure why.

I took the guts out and switched the lugs on the Bender pot - I did indeed have the + power coming from the DC Jack/Battery connected to Lug 2. Now it's on Lug 3 and Lug to goes to the 3PDT pcb. I'm not sure if that was the source of the popping or if something was making contact where it shouldn't.

However - In both configurations, the Starve/Bender knob did indeed dim the LED and affect the sound when starved, I assume since the LED was pulling what little power was coming through. This tells me I likely have something wired incorrectly. Maybe that's why I'm getting more oscillations than on my breadboard. Here are my connections:

DC Jack +9v > Lug 3 Bender pot
DC Jack Ground > a ground pad on the 3PDT pcb
DC Jack Sleeve > Positive battery snap (battery snap ground to Input Jack Ring)
---
Lug 2 Bender pot > a +9v pad on the 3PDT pcb
Pad A-1 on Vero > another +9v pad on the 3PDT pcb (it would normally connect directly to Bender Pot Lug 2)

*I have the feeling maybe the above +9v connections are incorrect...
---
Input and Output jacks > the designated areas on the sides of the 3PDT pcb
---
Attack Pot Lug 3 > Board Input pad on 3PDT pcb

Volume Pot Lug 2 > Board Output pad on 3PDT pcb
---
Attack Pot Lug 2 > Pad B1 on Vero

Volume Pot Lug 3 > Pad G1 on Vero

Gain Switch Lug 1 > Pad F1 on Vero
---
Ground connections from Vero H1, Volume Pot Lug 1, Attack Pot Lug 1, and Gain Switch > Ground pads on 3PDT pcb
---

Thanks for your help, Robert! Sometimes the pairing of vero/perf and these utility 3PDT boards can be a bit confusing - especially with all of the weird pot-based connections in this layout!

 

[Robert]

However - In both configurations, the Starve/Bender knob did indeed dim the LED

Something must not be wired exactly as intended.

The LED should be effectively connected directly to the DC jack (when connected to lug 3 of the starve pot).

The LED branch should have the full capacity of your power supply available (and not be affected by the Starve pot) because it completely bypasses the starve pot altogether.

 

[Ginsly]

Something must not be wired exactly as intended.

Almost certainly. Would you mind taking a quick look at my connections in that list and see if something stands out? That asterisked Bender/3PDT/Vero section is where I assume the problem must lie…

It seemed weird that I had to use two of the +9v pads on the 3PDT pcb… I just couldn’t see any other way to do it.

 

[Ginsly]

@Robert judging by your diagram (thanks for that, btw), can I simply take two separate wires from the positive lug of the DC Jack? One will lead to Bender Pot Lug 3 (Bender Pot Lug 2 will now connect directly to pad A1 on the Vero), and one will lead to a 9v pad on the 3PDT pcb. Not entirely sure if that's correct.

 

[Robert]

Yep, that sounds correct.

 

[Ginsly]

Yep, that sounds correct.

Thanks Robert! Good to know - I've never done that before, and actually didn't realize you could take more than one lead from 9v. Who knows, maybe the way I have it set up is contributing to those low oscillations too..? Guess I'll find out!