is there a way to "debounce" a pot?

[pinkjimiphoton]

You could always try your luck with a wirewound pot.  They don't have some of the failure modes of a carbon pot.  There used to be a series of pots where you could mix and match one pot to another so you could have a wirewound pot ganged to a carbon pot with any taper, shaft length or style you wanted.

i DID find a place where you can order these kind of parts yesterday, when i get down to my bench computer i will post a link.
if i go that way, i'll have to reverse the sections of the pot tho, and start with 1m then add a 20k <closest they got> for the wah.

tony pepers built me up a pair, down in new zealand you can still buy parts for this stuff, he'll be sending it to me soon, worst case.

[pinkjimiphoton]

Well, in this case it could in deed be a leaky C11 or C13? (letting some DC through)

It wouldn't hurt to try adding a 1uF poly cap  between pot pin 2 and ground, instead of just connecting pin 2 to ground.

If mechanical cleaning of the wah-pots carbontrack & wiper (!) won`t help enough, you could try if it evens out a bit, by hooking up 2 resistors (100k-330k) from the outer lugs (1, 3) to the wiper (2) of the wah-pot (R19).

Another trick is to add a 1M resistor between pin 2 and 3, and/or pin 2 and pin 1.
[Sorry, I read over the thread puretube already mentioned this one.]

Yet another idea would be to wire the pot back to the join of C4 and C5 instead of ground (via added 1uF cap on pot pin to 2).

These are all last gasp attempts to fend off crackly pots.

Edited

rob, i don't understand why adding a cap from pin 2 of the wah to ground would help?

i haven't tried tapering resistors yet to see if they'll help, i can try and get to that soon, in the middle of a production run for mla.

i'm thinking more and more its the circuit doing this. for instance, when the pedal's upside down, like, treadle on the bench? i get no scratchy scratchy at all.

wondering if this is why they added them diodes to the end of the fuzz circuit, maybe the square waving has something to do with noise reduction.... grasping at straws here lol

[pinkjimiphoton]

Coming back to the "missing diodes". According to the schemo (WITH diodes), the output of the Fuzz would be ~ 0.7V max across the Fuzz-Vol pot. If these diodes are omitted (still assuming we`re talking about the provided schemo), the full output-swing of the lower opamp`s pin7 (probably close to 9V!) will be across the Fuzz-Vol pot. - While this might give a "nice" overdriven opamp-fuzz sound in itself, this is much too much input-voltage for the wah-section, which, when the Fuzz is switched OFF, normally gets it (low-level) input directly from the guitar.
In such an overdriven situation, that filter operates beyond all specifications and acts strange, with the signal causing spikes bouncing against the supply-rails. (And sounding "flatter").
So it would be interesting to observe the overall-volume differences of the pedal (in the "now" state), with Fuzz on/off, Fuzz-Vol up/down, Signal-Mix up/down (all while the overall-Vol and the Wah-Vol pots rest in a middle-position. (Without sweeping the Wah, which otherwise also would change the overall-Vol).
If there`s a crazy level-difference between Fuzz On/Off, that`s not typical Fender-style ...
Ya see: I`m still in search of the lost diodes ...
(you could alligatorclip or solder 2 diodes across the Fuzz-Vol pot`s outer lugs and test the situation).

there's a volume pot for the fuzz level, so you can have the fuzz anywhere from barely on to rip your head off. when the fuzz is on, the volume treadle works as a master volume for the fuzz/dry mix. when ya turn the wah on, its fuzz and wah with no volume.

but i think ya hit on something there...spikes in the filter cuzza the extreme output of the fuzz....which strengthens my suspicions its a weirdness of this particular circuit!!

and nope, not a diode in sight anywhere in the circuit, including underside of the board. no holes for it either. so that makes me suspect this is a very early example of the circuit. the schematic is dated 73, supposedly these didn't come out til 74, which makes me wonder. i mean, we've all found unexpected things in vintage stomps...

so maybe the diodes were added specifically to remedy this by neutering the fuzz?

[pinkjimiphoton]

@Antonis, hahah, yeah, probably shoulda added them, but figured if they ain't there, there's probably a reason for it.

i have another coming in for maintenance from someone... i'll compare the two when it arrives. i bet the repair will have the diodes. we'll see!

[puretube]

Jimi: that`s what I meant: extremely loud Fuzz (as compared to mere Volume-Pedal or Wah-Pedal) is not Fenderish.
Maybe they took a PCB they had at hand already, and upped the feedback-impedance of that lower opamp, and soldered the ("smoothing, in this case) diodes onto the pot-lugs, to get an additional "Fuzz"-feature ... (?)

[pinkjimiphoton]

nope, i've had it all apart. its a brutal sounding fuzz, too... maybe a prototype?

[pinkjimiphoton]

roll your own pots

http://www.oldradioparts.com/pg2a22.htm

http://www.oldradioparts.com/2a22fil.txt

1502 is where the diy multisection stuff begins

[Rob Strand]

rob, i don't understand why adding a cap from pin 2 of the wah to ground would help?

The cap only helps if you have leakage (as per puretube's comment).  You can have leakage through the caps or on PCB surface.

i haven't tried tapering resistors yet to see if they'll help, i can try and get to that soon, in the middle of a production run for mla.

The resistors can help a bad pot but they can't fix it.   If you imagine a bad jack, the signal goes off and on and it sounds crackly.   A bad pot connects and disconnects in a similar way, adding the resistors reduces the amount of disconnection.

i'm thinking more and more its the circuit doing this. for instance, when the pedal's upside down, like, treadle on the bench? i get no scratchy scratchy at all.

Yeah, that's very weird.    I was thinking a bad pot, since the spray did something, but maybe there's a bad solder joint somewhere.  Poke around or tap on the PCB to try to provoke the bad spirits  .

[pinkjimiphoton]

pcb is good, wondering if its from the treadle being a bit worn, it can wiggle a little side to side, but the way the pot is hooked up that shouldn't really matter i wouldn't think....

[Rob Strand]

pcb is good, wondering if its from the treadle being a bit worn, it can wiggle a little side to side, but the way the pot is hooked up that shouldn't really matter i wouldn't think....

One criticism of the design of the circuit is, when the wah pot wiper is at the pin 3 extreme it is shorting the C13 cap across the opamp output (pin 1).   That's a good way to make the circuit oscillate which can appear as crackling.  As a start, you could try adding a 1k between E6 and pot pin 3, or between pot pin 2 and ground.   If that does something try to reduce the value as much as possible, perhaps stopping at 100R to 220R.

Technically speaking you should have a resistor in series with the opamp output as well, like R25 on the CE2,
https://www.hobby-hour.com/electronics/s/boss-ce2-chorus-schematic.php

However, if you back off the wah volume pot from full a tad it should add that resistor by default.   Backing off the wah volume pot can't help the C13 issue though.

I hate debugging these circuits with minor design issues.   They are either the cause outright or they put you on the wrong path.

[PRR]

> http://www.oldradioparts.com/2a22fil.txt
1502 is where the diy multisection stuff begins

FWIW: Gary passed away in 2020. Someone else took over the business but has not, apparently, re-opened. (I think Gary kept much of it in his head.)

[pinkjimiphoton]

> http://www.oldradioparts.com/2a22fil.txt
1502 is where the diy multisection stuff begins

FWIW: Gary passed away in 2020. Someone else took over the business but has not, apparently, re-opened. (I think Gary kept much of it in his head.)

oh, shoot... so sorry to hear, paul. thanks for the headsup.

rob, i will give that a shot. when i take it apart next time, i'm gonna remove the footswitches, drive the treadle pin out, and add another washer or two to tighten up the treadle, which kinda "wobbles" a bit side to side from wear... which may also be what's causing the weirdness.

i do believe you may be right about the oscillation. the repair one i'm doing for someone came in yesterday, i'll see if it does the same... if it does, we'll know conclusively if its the circuit or not.

the fuzz from this pedal needs to be isolated. its truly a great fuzz. i believe gus smalley and i did it about 10 years ago, i gotta look.....

founded it. the vero is verified, i built several of these years ago. don't bother with the dry blend, it doesn't work for shit.






from 9 years ago... tempus fugit

[Rob Strand]

rob, i will give that a shot. when i take it apart next time, i'm gonna remove the footswitches, drive the treadle pin out, and add another washer or two to tighten up the treadle, which kinda "wobbles" a bit side to side from wear... which may also be what's causing the weirdness.

i do believe you may be right about the oscillation. the repair one i'm doing for someone came in yesterday, i'll see if it does the same... if it does, we'll know conclusively if its the circuit or not.

I guess you will have to poke around and try a few things.  Not a straight forward problem.

A few times in the past I've stuffed about trying to track down fizzy sounds and it turned out to be bad connections on the input or output sockets.    Sometimes turning things upside down can affect how the connections are made at the socket because the cable hangs differently and changes how the jack pushes against the socket.  Another time there was a loose earth connection on the bridge on a bass.   Yeah, I know, in your case the sockets don't quite make sense since cleaning the pot had the most effect.

[pinkjimiphoton]

ok, in a new plot twist,
pink jimi notices a curious lump in a bin of pedals

its another one of these fuzzawahwahvolya pedals. this one is POLISHED <and tarnished> aluminum but effectively the same circuit, inside.

so i plugged it in. shit, i didn't even remember owning it, at first. works perfect. wah sounds great. get some weird resonances that are similar to the ones in the other one. i think its a MECHANICAL issue now, for sure... that combined with the resonance of the filter seem to be hand in hand. so i'm gonna remove the footswitches on it, drive out the pin and reconstruct with some washers or something to make the pedal tighter and see if the issue goes away, this one's sweep has NO left to right wiggle at all.

stay tooned-ish

[pinkjimiphoton]

ya know, sometimes our forefathers have vision...

so i took a bumm screwdriver and a hammer and, after removing the two stompswitches,  drove the pin out of the treadle enough to kinda work in two thin ss washers on one side, hoping that that would tighten up the treadle sweep. it did, but not enough, really.
there's nylon bushings inside the thing i didn't wanna deal with.
drove the pin back in, way less wobble. still too much tho.

and THEN CAME THE EPIPHANY

look at the other one, ya pink dumbass

and lo and behold, unnoticed previously, the great one, dare i say his godlike name

clarence... mr fender


had angled the goddamned footswitches,

the corner of the footswitch is supposed to ride against the side of the stomp as the treadle sweeps up and down.

did that too offending fuzzwah

after weeks of dicking around, trying to think electrical

it was a mechanical situation. once i angled the switches slightly, no wobble, and the wah and fuzz now work well together when on.
still a bit of nasty resonances now, but no more scratchy scratchy.

there's a sweet spot where it drags just barely so the wah can stay fixed, or swept. tiny tiny bit of mechanical scrape, but doesn't pick up
thru the circuit.

i'd call it a win-win

at all of the controls half way up, you can torture a fender style amp with your guitar. just turn it up and down. from clean to barely overdriven to absolutely screaming.

i'm gonna keep this one for ME.

thanks guys !!!!! <3

[Rob Strand]

ya know, sometimes our forefathers have vision...

Cool story.

It's all to easy to look at something that works and assume how obvious it is.   It's not until you come across something that also also looks like it works but doesn't that you begin to appreciate what it takes to get something working!    It reminds me of all the "expert" advice that gets thrown around in meetings and two minutes after going back to your desk you realize it doesn't help.   Forums can get like that too  .