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.

 

[comradehoser]

Fired it up last night and decided to clip the input jack to ground just to see if it made a difference.

Sounded good and no weird volume swells, even when voltage was fully CCW and gains were all the way up. Definitely a creamier tone with the smd "in-spec" j201s vs the interfet "out-of-spec" through-hole j201s. I actually don't know which I prefer, though.

But then, I moved the pedal, plenty of crackly noises and a drop in volume, so I am pretty sure that there's an offboard wiring issue, maybe a grounding issue. I will also revisit my original pedal's grounds to see if that can fix the strange volume fluctuations.

I'm guessing maybe it's a voltage reference issue that becomes a problem when the transistors are getting a bit starved and still pushing higher gain. Like they can't detect the reference floor at ground, so the output starts floating along a sine wave. It's what it sounds like, anyway. I am definitely not an electronics engineer, so somebody please feel free to correct my dumb idea.

 

[box1gosrgo]

quick tip for when you accidentally fill a hole- heat it up and stick a toothpick into the hole. clears it easily

 

[comradehoser]

Excellent! Will try

 

[Giorfida]

Fired it up last night and decided to clip the input jack to ground just to see if it made a difference.

Sounded good and no weird volume swells, even when voltage was fully CCW and gains were all the way up. Definitely a creamier tone with the smd "in-spec" j201s vs the interfet "out-of-spec" through-hole j201s. I actually don't know which I prefer, though.

But then, I moved the pedal, plenty of crackly noises and a drop in volume, so I am pretty sure that there's an offboard wiring issue, maybe a grounding issue. I will also revisit my original pedal's grounds to see if that can fix the strange volume fluctuations.

I'm guessing maybe it's a voltage reference issue that becomes a problem when the transistors are getting a bit starved and still pushing higher gain. Like they can't detect the reference floor at ground, so the output starts floating along a sine wave. It's what it sounds like, anyway. I am definitely not an electronics engineer, so somebody please feel free to correct my dumb idea.

I’d bet the difference in tone between the j201 SMT vs Thru-hole is less about the packaging and more about bias

 

[comradehoser]

quick tip for when you accidentally fill a hole- heat it up and stick a toothpick into the hole. clears it easily

This didn't work so well for me

 

[comradehoser]

Un-SOLVED!-ing the thread.

Managed to get the hole cleared and capacitor seated.

Instead of volume swells, I am getting randomly intermittent frottage/static storms and pops. They drop volume (and the volume is super high!)

Checked continuity with the through hole pads on the SMD j201s, checks out. Cleaned around the SMDs.

Subbed out the charge pump for another ICL7660SCPAZ. Now I have intermittent static storms and brutal charge pump whine.

Visual inspection of what I can see in terms of soldering checks out, although the j201s could have been centered better.

I'm guessing a bad pot or one of the SMDs is toast/poorly soldered?

Any special advice for desoldering SMDs if it comes to that?

 

[szukalski]

. Check the SPDT toggle switches are not shorting against the pots. I had to put something in between them on my build. It’s a tight one, control wise.

 

[comradehoser]

I checked to ensure a gap, but will remove all washers just to make sure they are not gallivanting about.

 

[jwin615]

Is that a metal DC jack? If so, is the outside isolated from the positive rail?

 

[comradehoser]

No, it's a regular black jack.

Reflowed grounds connections, pot legs, and the charge pump sockets. Removed all washers from toggle switches even though there's a 1mm gap

Worked great for a bit. Then, the crackle and pop starts up again for no apparent reason. Kinda puzzled on this one. Bad DC Jack?

 

[comradehoser]

Tried a new DC Jack. Worked great for about 10 minutes, and I thought it was all good and resolved.

Alas, no.

After our static storms, I pushed on every component with a toothpick, no correlation.

It's pretty random other than time. Seems like something is getting too hot and expanding and touching parts that shouldn't be, or is improperly accumulating charge and discharging into the circuit randomly.

Here's a link since the file is too large to insert, apparently:

Me noodlin

You can hear the signal ducking under the static when I turn down the voltage with the center top pot.

 

[jwin615]

Is the charge pump getting real hot?
Any of the pots crackle when you turn them?

 

[comradehoser]

Charge pump: not really [definitely not--just ran it for 30 minutes and it's stone cold]. In the video, I turn pots and noise happens, but it doesn't really correlate. It continues and stops independent of touching or manipulating anything. It starts when I touch pots, it starts when I don't touch pots. I really can't puzzle this one out

 

[jwin615]

Hmm. Did you match/pick the J201s for spec?

 

[comradehoser]

Nah. I figured SMD would be good to go/tight on the specs, but maybe that's an incorrect assumption. You think an hfe mismatch would cause pops and static after operating well for a while?

 

[music6000]

A crappy footswitch can also cause static issues???, click it on & off a dozen times & se if it changes anything.

 

[jwin615]

Nah. I figured SMD would be good to go/tight on the specs, but maybe that's an incorrect assumption. You think an hfe mismatch would cause pops and static after operating well for a while?

Not necessarily. They tend to be tighter though.
Crackling is often a non-solid connection though, be it mechanical or soldering. It can also be DC on pots, but that's usually more of a noise when turning deal in my experience. I know you reflowed a bit already but I'd take a long hard look at your smd joints. I know you said you poke around with a toothpick. The eraser end of a good ole number 2 is a little better. Want to put some stress on the joint to try and break it more, basically. Chop stick works good to. Could also be a switch as music6000 mentioned. Try bypassing a few times when it's making noise.
Maybe sweep your iron between solder pads making sure there's not a hairline of solder somewhere. Been there.
Also. Don't discount a bad patch cable. Been there too. Almost returned a guitar I had flown overseas over a bad cable. Worked fine without issue until the day that guitar showed up.

Beyond all the above, gonna need to probe it and isolate at least the section of the circuit it's coming from.

 

[comradehoser]

All actionable and useful advice! Thank you much, will definitely run through everything

I also concur that static is an improper connection but I checked through my offboard solder points and they look good. Have never had a bad 3pdt up to this point. The thing that puzzles me is why it seems fine at first and only seems to develop crackle storms after some time. That's what pushed me towards thinking more towards component issues

My smding was a little less than optimal, but all joints registered continuity. What should I be looking for a good/not good joint?

[Edit: definitely not a bad patch cable. Run other pedals through the same rig no probs]

 

[szukalski]

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