DOD FX-17 Wah/volume - how does it work?

[O]

I got a broken fx17 and I opened it up last night only to find out that it doesn't use pots, optical, or any other "mechanism" that I'm aware of. Does anyone have any clue how this thing is supposed to wah and control my volume without pots? I'm stumped...

(magic maybe? :? )

[Paul Marossy]

I have one of these and have wondered about how they work as well. I think they use the Hall Effect, but I have not verified this.

How is it broken? Does it do anything at all?

[O]

When you move the pedal up and down, it makes a sort of wah/underwater chirping sound :?

At first I thought it was optical, but once I took the top cover off, I was more than a little stumped. I tried looking on the net for clues but all I can find is the DOD description and nothing else.

[Paul Marossy]

Yeah, there are no schematics available for it that I have ever seen. Unfortunately, I can not be of any more help on this one...  

[O]

Yeah, there are no schematics available for it that I have ever seen. Unfortunately, I can not be of any more help on this one...  

Well I opened the battery compartment and I swear I saw an elf and a gnome fall out (otherwise, how else would this thing work) :lol:

I'm going to start tracing it out to see if it makes any more sense... I'll keep y'all posted.

[Paul Marossy]

I'd be very interested to see what you come up with!  

[12afael]

I buy one for 5 dollars.
I wished to use the box for a cry baby clone. but it don`t have a pot, it use a variable cap formed by a sheet of metal a plastic dielectric and a circuit board with a pattern (no lineal).
I suppose that the circuit is a twin-T but without the schematic I can`t be sure.

[Paul Marossy]

I buy one for 5 dollars.
I wished to use the box for a cry baby clone. but it don`t have a pot, it use a variable cap formed by a sheet of metal a plastic dielectric and a circuit board with a pattern (no lineal).
I suppose that the circuit is a twin-T but without the schematic I can`t be sure.

Ah, that makes sense. That plastic/metal part was the mysterious part of that pedal to me. I like it because there is no pot that will ever get worn out. I suppose that plastic can get worn out, though. Hmm, hey O, maybe that is your problem?!

I'll agree that the circuit is probably a twin-T type of circuit - I don't remember seeing an inductor in there...

[David]

Do the plastic and metal layers form a sandwich?  I wonder if the thing could actually be a capacitor... perhaps even variable?

[Paul Marossy]

Do the plastic and metal layers form a sandwich?  I wonder if the thing could actually be a capacitor... perhaps even variable?

Yes, they do form a sandwich. When you move the foot paddle up/down, it changes the relationship between the steel and copper plates, and the plastic in between them is the dielectric. I think it's actually something like 1 mil mylar. Anyhow, it's definitely a variable capacitor. It sure would be interesting to see a schematic for it - but I'm not motivated enough to look at mine an create one.  :oops:

Oh darn, I think I feel a new webpage project coming up.  :x  :wink:  :lol:

[Stompe Le Monde]

This is probably the only wah pedal that I like and use, well, out of all the commercial wahs I've used at least.

I traced it out a long while ago, I'll post it if I can find it after some light digging...

[Paul Marossy]

This is probably the only wah pedal that I like and use, well, out of all the commercial wahs I've used at least.

I traced it out a long while ago, I'll post it if I can find it after some light digging...

That would be most cool if you could find that and share it with us!  

[12afael]

yeah .try to find it!

mine don´t sound very cool I think . is really hard set up the internal trim pots to get a good feel .

I buy it dead . the top should be conected to ground for proper work of the cap(If I remember well). the little momentary switch could be damage too.

[Preben Hansen]

Look in Schematics2, under DOD Wah Volume. This schem has been there for a long time.
/Preben

[Stompe Le Monde]

Haven't found it yet, though I have about 4 more boxes to go.  The one listed as "DOD Wha Volume" looks correct at first glance.  I'll keep looking for mine though...

I do love the sound of this thing though, it's much more harsh and synthetic sounding than most any other wah out there.  It's great when I feel the urge to try and emulate Joey Santiago, which is actually pretty frequently.

[Paul Marossy]

Look in Schematics2, under DOD Wah Volume. This schem has been there for a long time.
/Preben

It is?! Got a direct a direct link to it? I sure as heck can't find it there...

EDIT: Never mind, I just found it.  :oops:

[12afael]

http://www.diystompboxes.com/cgi-bin/webbbs_scripts/webbbs_config.pl?read=201

cool!