Fulltone Clyde Standard Wah Reverse Engineering.

[Andr3as]

Hey!
Got a defekt pot on my fulltone wah, and was about to replace it when i wanted a schematic of this expensive wah circuit.
So i took it apart yesterday and started drawing, first time I've done a reverse engineering! phew....

Anywho, here's a link to the schematic (I still don't know how to insert images ):
https://www.dropbox.com/s/owpcv4d46e030aa/2012-07-31_16-28-34_907.jpg




Will be doing a PCB layout later tonight from the original PCB... The circuit is VERY close to a standard VOX V847.
I'm not completely sure of the 1k resistor at Q1's emitter.. It MAY be 100 ohm, I will double check that.
Let me know if you guys can't see the schem.

[joegagan]

yes, it is a great exercise to draw out a circuit. looks like you have done a good job. my guess is that the 1k at E>gd @ Q1 is 100 ohm. unsolder one side off the board and measure ( sometimes the markings on reistors can be deceiving or hard to read)

otherwise, a bang on clyde circ. mike knows how to leave a nice circuit as designed. good parts, good assembly, happy customers.

[Andr3as]

1k seems a bit high, carbon comp resistors are very hard to read!
Thumbs up for fulltone, high quality products all the way..

I'm doing a PCB layout now at DIYLC, Looks very close to the original. I will post it later.. I need to check some resistor values first

[Andr3as]

PCB layout:


PCB print file (pdf)
https://www.dropbox.com/s/b7fy6cr8jcherx8/Fulltone%20clyde%20pcb.pdf

1k resistor from the schematic changed to 100 ohm in the layout
The layout is very close to the original and the board measures 68x58mm..

Cheers!

[Nocaster Cat]

I'm a little confused about the 2k trimmer in parallel with the 470r resistor as it seems like one part too many. Could he not have gotten away with a 500r trimmer and pretty much accomplished the same thing? Also, do we know what transistors are used for Q1 and Q2? Thanks!

[joegagan]

nocaster, i can't say for sure,
my guess is that fuller was trying to make it idiot proof to prevent tones that would cause customers to call and say their pedal wasn't sounding right.

this makes a lot more sense if the resistor at E of Q1 was 100 ohm instead of 1k.  

[Paul Marossy]

I'm a little confused about the 2k trimmer in parallel with the 470r resistor

Yes, that is a little weird. Seems like they should be in series so that it can never go below a certain value rather than in parallel, which doesn't make much sense to me.

nocaster, i can't say for sure,
my guess is that fuller was trying to make it idiot proof to prevent tones that would cause customers to call and say their pedal wasn't sounding right.

Maybe. Assuming the schematic is correct and they're not in series instead. That would make more sense to me. Unless its some kind of trick to get the trimmer to be a 400 ohm trimpot. That could also make sense I guess....

[alexradium]

nocaster, i can't say for sure,
my guess is that fuller was trying to make it idiot proof to prevent tones that would cause customers to call and say their pedal wasn't sounding right.

this makes a lot more sense if the resistor at E of Q1 was 100 ohm instead of 1k.  

yes that resistor is 100 ohms,i had the deluxe version,so you can get a range from 100 to around 500,which is ok for that tranny,best value is around 300/350.

[alexradium]

I'm a little confused about the 2k trimmer in parallel with the 470r resistor as it seems like one part too many. Could he not have gotten away with a 500r trimmer and pretty much accomplished the same thing? Also, do we know what transistors are used for Q1 and Q2? Thanks!

in my deluxe trannies were 2SC828

[Paul Marossy]

nocaster, i can't say for sure,
my guess is that fuller was trying to make it idiot proof to prevent tones that would cause customers to call and say their pedal wasn't sounding right.

this makes a lot more sense if the resistor at E of Q1 was 100 ohm instead of 1k.  

yes that resistor is 100 ohms,i had the deluxe version,so you can get a range from 100 to around 500,which is ok for that tranny,best value is around 300/350.

So then the 2K trimpot in parallel with the 470 ohm resistor is a trick to make that trimpot look like a 400 ohm trimpot to the circuit. Makes sense now.

[joegagan]

nocaster, i can't say for sure,
my guess is that fuller was trying to make it idiot proof to prevent tones that would cause customers to call and say their pedal wasn't sounding right.

this makes a lot more sense if the resistor at E of Q1 was 100 ohm instead of 1k.  

yes that resistor is 100 ohms,i had the deluxe version,so you can get a range from 100 to around 500,which is ok for that tranny,best value is around 300/350.

So then the 2K trimpot in parallel with the 470 ohm resistor is a trick to make that trimpot look like a 400 ohm trimpot to the circuit. Makes sense now.

you got it. two possible reasons he went with 2k and a limiting resistor: 1. he liked the way the pot worked, ie; gave the user a better adjustability, or 2, he got a smoking deal on a bunch of 2k trimmers. we know trimpots cost WAY more than the 470 ohm resistor.

[alexradium]

nocaster, i can't say for sure,
my guess is that fuller was trying to make it idiot proof to prevent tones that would cause customers to call and say their pedal wasn't sounding right.

this makes a lot more sense if the resistor at E of Q1 was 100 ohm instead of 1k.  

yes that resistor is 100 ohms,i had the deluxe version,so you can get a range from 100 to around 500,which is ok for that tranny,best value is around 300/350.

So then the 2K trimpot in parallel with the 470 ohm resistor is a trick to make that trimpot look like a 400 ohm trimpot to the circuit. Makes sense now.

you got it. two possible reasons he went with 2k and a limiting resistor: 1. he liked the way the pot worked, ie; gave the user a better adjustability, or 2, he got a smoking deal on a bunch of 2k trimmers. we know trimpots cost WAY more than the 470 ohm resistor.

maybe it was just the big knob,you can turn it by hand,no mini screwdrivers,much more robust

[Andr3as]

I think he's trying to limit the range to not let the wah sound crap...


Gut shots both sides of the pcb
https://www.dropbox.com/s/jwvtm57ox1hemc8/2012-07-30%2023.29.27.jpg?m
https://www.dropbox.com/s/qlinefgue25sw24/2012-07-30%2023.29.50.jpg?m

[Nocaster Cat]

nocaster, i can't say for sure,
my guess is that fuller was trying to make it idiot proof to prevent tones that would cause customers to call and say their pedal wasn't sounding right.

this makes a lot more sense if the resistor at E of Q1 was 100 ohm instead of 1k.  

yes that resistor is 100 ohms,i had the deluxe version,so you can get a range from 100 to around 500,which is ok for that tranny,best value is around 300/350.

So then the 2K trimpot in parallel with the 470 ohm resistor is a trick to make that trimpot look like a 400 ohm trimpot to the circuit. Makes sense now.

That's my guess. 2k + 470r in parallel should yield 390r which when in series with the 100r would yield 490r.