SOLVED Deofol--my other problem child

[comradehoser]

Built the Deofol for a second time for a friend with smd j201s. Have smd'ed successfully before (I think).


Sounds good-- very comparable to the first pedal, except that the distortion "grains" are a bit tighter with the smd j201s and the pedal sounds a bit more saturated than my first build with interfet through-hole j201s.

However, I am getting very strange volume swells across settings. This happens in my first build, but only if the voltage knob is set to 9:00 or lower, and the gains are set higher than noon. I am guessing maybe my smd skills are not so great after all, or it's a capacitor issue (?) or ... maybe the charge pump isn't right?

A strange event that may or not be related to this behavior: in a first for me, I managed to inadvertently fill a pad on C21 (10nf, lower right), and could not dislodge the solder for love or money with "heat-and-smack," more solder, more flux, solder sucker, or even pushing through a component leg. Could not get the cap leg through or extract it once it bonded with the solder, so I just left it after it tested positive for continuity. C21 looks like it is one of three caps wired to ground for the mids switch, so I fail to see how it would cause volume swells over the entire circuit.

 

[jwin615]

You’re not using any material between the pots and the PCB?

Doh!

 

[comradehoser]

Yes, I am using dustcovers, but only on the pots actually laying on the PCB.

The ones hanging off the board aren't contacting anything

 

[music6000]

As szukalski pointed out, make sure the Pot legs on the Level & Feed pots are not touching the metal plate on the side of the toggle switches when you tighten it in the enclosure???
A test would be to loosen the nuts and jiggle the pots to see if it has an effect???

 

[comradehoser]

Yup, been jiggling pots (you can see it in the vid). No correlation.

Here's a side view so the toggle-pot gap and pot doilies are obvious [edit: Playboy soft focus shot unintentional]

 

[music6000]

Curious, was it the top pad of C21 that goes to the mid switch that gave you trouble?
Did you check to see if that same pad was going to Ground with the continuity test?
It would only cause an issue when switched to that position if faulty.

The Solder side of the PCB looks like it needs a good clean, lots of little debri on it that may cause issues.

 

[comradehoser]

Curious, was it the top pad of C21 that goes to the mid switch that gave you trouble?
Did you check to see if that same pad was going to Ground with the continuity test?
It would only cause an issue when switched to that position if faulty.

The Solder side of the PCB looks like it needs a good clean, lots of little debri on it that may cause issues.

Yes, it was c21, and I had the same conclusion as you did. I did test its connections anyways to see if they were the issue, and they were fine.

I hear you on the cleaning. I recleaned in my troubleshooting after the shot. Will do my best because I can't lift the lower pots obstructed by the toggles

 

[comradehoser]

Well, it's been 45 minutes of solid playing, and .... NO static!!!

Eagle eyes Music6000, Szukalski, and jwin for the win, as usual. Thank you really sincerely for your time, ideas, and analysis. I really appreciate it! I learn a lot from you pros.

Here's what I did: went through suggested troubleshoots in order, first up was jwin's suggested SMD inspection. Which was not easy for Q1&2, tucked away as they are in a capacitor nest, which is why i may have missed that the gate tab on both was looking a little meager in the solder department. AND Q2 had a fibre or hair to boot.

(I think I had forgotten to solder in the SMD's until after the caps were in, which was very awkward and maybe contributed to a poor joint--looked good from a distance, but a bit dodgy under magnification--always remember your order of assembly, kids! Lowest to highest!)

Guessing at best practice, I hit them both with a good dab of flux and a drop of fresh solder, cleaned around with my iron tip, and... Voilà! No more crackle storms.

So, in the end it was a poor connection and component issue.

Hopefully this time this buddy will stay solved!