need to find a stacked pot....

[pinkjimiphoton]

for a fender fuzz wah, one of the ones with the dualie op amp.

the pot is wasted, pretty much. i took it apart and cleaned it, and got the 1meg part working perfectly... but the 10k pot side for the wah is on acid.

it does a sweep from bass to treble, then back to bass. i've encountered this before in a crybaby, and it was the "stop" was in the wrong location on that... re-orienting the metal cover fixed it right up. this time, no such luck so far.

i have some similar pots, 50k and 5k, figuring i may have to do some surgery to make it work and graft parts from other pots to the one in the pedal. i realize the sweep may be a little funky if i add a resistor, so i'd like to get it right if possible.

does anyone know where i can find a stacked 1m/10k that isn't insanely expensive?

advice appreciated!!

here's the schematic, if anyone is interested.  this one has a 4558 in it that looks like someone replaced the original chip with (socketed).



the fuzz sounds killer... thick and dark and smooth... very guitar solo on inna gadda da vida-ish. and the wah, if it worked, would sound great, a much wider sweep than the usual crybaby or morley.

[psychedelicfish]

do you mean a wah pot, or a standard knob one? I might have something useful in my collection, I'll have a look when I get home

[psychedelicfish]

looks like you need a wah pot. I might have a standard pot with those values which you could attach some kind of gear to. You might be able to stick a buffer before the 1M pot and just use a 10k dual gang pot though

[digi2t]

The only thing I can thing I can think of is using two Omeg pots, and grafting one half to the other. Since they're modular, You could drill out the rivets, swap out one of the pots, and the rivet it back together. This is the type of pot that I used for the Vocalizer.



Not a "super cheap" solution, but cheaper than some special order PEC unit.

[pinkjimiphoton]

looks like you need a wah pot. I might have a standard pot with those values which you could attach some kind of gear to. You might be able to stick a buffer before the 1M pot and just use a 10k dual gang pot though

thanks ed, if you could see what you have, i'd appreciate it!!



ideally, i'd like to keep this thing as close to stock as possible. it's a really nice sounding pedal.

yes, it's a wah style pot, but stacked... 1 meg closest to the shaft, and 10k behind it. i'm not done playing with it yet.
i had this exact problem once before, and fixed it. i should do a search and see if i can find what i did.

[pinkjimiphoton]

The only thing I can thing I can think of is using two Omeg pots, and grafting one half to the other. Since they're modular, You could drill out the rivets, swap out one of the pots, and the rivet it back together. This is the type of pot that I used for the Vocalizer.



Not a "super cheap" solution, but cheaper than some special order PEC unit.

i've still got a couple of them from the vocalizer build too, dino. good idea!!

but... found my old thread..

http://www.diystompboxes.com/smfforum/index.php?topic=101925.0

and someone DEFINITELY monkeyed with both pots. so i'm thinking that the stop is wrong for the 1meg too, tho it seems to work right...
i'm gonna try and pop the back off the 1 meg pot as well as the 10 k, get the 10 k so it's sweeping right, and put the cover on it again.
hopefully, it won't mess up the sweep of the volume too much...i should be able to get the original spot back where both sides work hopefully!!

wish me luck, as soon as i finish this cigarette, i'm going in!!

on a personal note dino bro.... hope all is great!! let me know if you venture down this way this year!

[PRR]

[pinkjimiphoton]

paul, bless you man... thanks!! i see how to do it now... and it makes perfect sense, too. easy. elegant. AVAILABLE!   

BUT.....

i got it nailed man.... i was thinking about it and realized someone had monkeyed with the pots, and fail'd at heroism. they had the volume half clocked wrong, and the wah pot wired backwards, so treble was toe down. but in volume pedal mode, full volume would be toe down, same when the fuzz was on. i dunno about you, but that right there would drive me nuts completely...counterintuitive, it looks like it may have been the original wiring on it, but hard to tell on a 30 some odd year old pedal.

anyways, i turned the 10k pot until it was full treble when rotated all the way up... then set the "stop" or whatever you call it inside the pot  180 degrees off from what it was... i think when the previous owner had it, he tried to clean the pot, couldn't get it right and gave up in frustration. once the thing was together right, (cleaned/lubed well before buttoning up) it sounds great. i have to address a mechanical issue in the treadle, it wobbles a bit left to right, but once i sort that out, i'd say this thing will be a keeper.

i LOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOVE the fuzz in this thing. it is truly sick, and the wah sounds like a cross between a crybaby and a morley... really big range, uses the full rotation of the pot. nice pedal.

hopefully if anyone else encounters these kind of weird pot problems, they can fix it thru my lummoxxing.

i was surprised how easy it was to disassemble and repair, they're old ohmites and they appear to be tough as nails.

thank you guys for the help, and awakening the vague memory of dealing with something like this once before.

peace out... will try and get a little video once it's done. 

[wolfy]

A friend is going to give me one of these Fender Fuzz Wahs to repair as there is a problem with the dual pot. In the case that some cleaning does not do the fix - I am interested in your solution here. I just can't understand what you are saying to do in a practical sense. Anymore clarification would really help.

[pinkjimiphoton]

what paul is saying is to use a dual 10k pot instead of the odd value one,  take the circuit where it goes from the switch to the 1m pot, and simply graft a simple buffer in there. chip, transistor, whatever ya like... and then hook the output of the buffer up to the 10 k pot instead of the 1m.
the buffer will isolate the two parts of the circuit and raise the impedance enough that a 10k pot will work fine, or should.

if this has the original ohmite pots in it, you may be able to repair it if they aren't too wasted. but if they are, use paul's idea, and i bet it will work fine.

i never tried it cuz i fixed the original and flipped it a long time ago, but if ya looks at some schematics a while, you'll see this kind of use often.
in my case, glad you posted, cuz i have two huge bags of 10k full size pots someone gave me, and now i can see how i can use 'em.


i gotta get back into diy, been so busy doing repairs and custom guitars and amps and crap lately i haven't built a fuzz since like april. i am way overdue!!

the spirit is willing... i now have a huge shop with a nice bench to work... but it's like archaeology... i have to dig thru layers of blankets and comforters to buffer the guitars from all the crap on the bench. egads!!

[wolfy]

Thank you kindly, I appreciate your help so much Jimi.
So if need be:
1. Replace the old dual 10k/1m with a new dual 10k/10k.
2. I could use a transistor such as 2n2222a as a buffer in the said spot in the following way - Base to #5 on fuzz switch, Collector to #3 of Volume pot and Emitter to ground?

I am finally getting back into again after a hiatus. I am still an avid beginner but I am keen to keep learning.
All the best with your future projects, we just gotta get quicker and more organised!
Thank you,
Josh

what paul is saying is to use a dual 10k pot instead of the odd value one,  take the circuit where it goes from the switch to the 1m pot, and simply graft a simple buffer in there. chip, transistor, whatever ya like... and then hook the output of the buffer up to the 10 k pot instead of the 1m.
the buffer will isolate the two parts of the circuit and raise the impedance enough that a 10k pot will work fine, or should.

if this has the original ohmite pots in it, you may be able to repair it if they aren't too wasted. but if they are, use paul's idea, and i bet it will work fine.

i never tried it cuz i fixed the original and flipped it a long time ago, but if ya looks at some schematics a while, you'll see this kind of use often.
in my case, glad you posted, cuz i have two huge bags of 10k full size pots someone gave me, and now i can see how i can use 'em.


i gotta get back into diy, been so busy doing repairs and custom guitars and amps and crap lately i haven't built a fuzz since like april. i am way overdue!!

the spirit is willing... i now have a huge shop with a nice bench to work... but it's like archaeology... i have to dig thru layers of blankets and comforters to buffer the guitars from all the crap on the bench. egads!!

[nocentelli]

A buffer needs to be more like this:

http://www.muzique.com/images/buff6.gif

The vref could be the node between a voltage divider pair of 10k resistors.

[wolfy]

Thanks for clearing that up mate.
So in this case I could make a tiny little board including  and with the Vr points connected?
Thanks again, I am learning.

A buffer needs to be more like this:

http://www.muzique.com/images/buff6.gif

The vref could be the node between a voltage divider pair of 10k resistors.

[David]

Wolfy:

Go to the article "Basic Buffers" in the Lab Notebook section on www.muzique.com.  The fifth diagram is a bipolar transistor buffer that does not require a reference voltage source.  You could use that for simplicity, if you prefer.   I would suggest you use a 2N5088 or 2N5089 instead of the 2222, though.

[antonis]

Go to the article "Basic Buffers" in the Lab Notebook section on www.muzique.com.  The fifth diagram is a bipolar transistor buffer that does not require a reference voltage source.  You could use that for simplicity, if you prefer.   I would suggest you use a 2N5088 or 2N5089 instead of the 2222, though.

If the 100k input impedance is not a problem..

[wolfy]

Wolfy:

Go to the article "Basic Buffers" in the Lab Notebook section on www.muzique.com.  The fifth diagram is a bipolar transistor buffer that does not require a reference voltage source.  You could use that for simplicity, if you prefer.   I would suggest you use a 2N5088 or 2N5089 instead of the 2222, though.

Brilliant - if need be I will give that one a shot. Here it is -

Hmm as for the input impedance - I am not sure.

[pinkjimiphoton]

everybody else beat me to it.

yeah, wire it as an emitter follower.
i don'tthink ya have to worry too much about the source impedance there, anything over 10k should be fine i'd imagine. 220k is good.
you could go 100k to 1m and it will probably be fine... it's main purpose is just to isolate the switch and the pot.

i'd probably go with a higher gain transistor myself... hell, i'd probably wire it more as aboost.. i prefer being able to tweak stuff a little.. maybe put in a 5-10k pot instead of the e resistor to control the gain.... use a trimmer or something.

or use a FET or MOSFET... may work better. dunno. been a while since i messed with anything effect related, too busy with amp and guitar repairs in my shop since i moved to dick around with pedals much.

[David]

Go to the article "Basic Buffers" in the Lab Notebook section on www.muzique.com.  The fifth diagram is a bipolar transistor buffer that does not require a reference voltage source.  You could use that for simplicity, if you prefer.   I would suggest you use a 2N5088 or 2N5089 instead of the 2222, though.

If the 100k input impedance is not a problem..

How did you derive 100K for the input impedance?  Looks like it would be more like 220K.  'Course, as "jimiphoton" says, "I ain't no flippin' EE".

[pinkjimiphoton]

i'm guessing you could use two 47k instead of 200k if ya need a 100k source impedance maybe

[antonis]

How did you derive 100K for the input impedance?  Looks like it would be more like 220K. 

As long as we may consider the Power Supply as a source with zero resistance, it looks like we've got 3 resistances in parallel (220k//220k//3k3*Q1beta..) = < 100k