Amateur wah circuit troubleshooting?

[tommycataus]

I've attempted to build the Clyde McCoy imitation found on Fuzz Central:
http://fuzzcentral.ssguitar.com/mccoy/mccoylayout.gif

The true bypass works fine, but when switched on the circuit squeals. It is constant and nothing changes the sound i.e. when the wah is rocked. The only thing that alters is the pitch when I switch between single coil and humbucker configuration on the guitar.

I've checked the voltage between ground and terminals 1, 2 and 3 and for each it is equal to zero, however when engaged the battery is getting extremely hot and has gone from 9.6V to 8.4V in less than 5 minutes so I don't want to keep checking voltages for each and every connection if it means keeping it all connected. Further than that I've double checked that my vero layout has been followed exactly, so my circuit is as it appears below:



I've triple checked solder joints and accidental grounding issues.  I'm almost certain I've made a mistake in the translation of this PCB layout to vero and after checking thoroughly I can't see where. Rookie mistake: I am still waiting for my breadboard to arrive and I couldn't wait  Can anyone help?

[tommycataus]

I should add that for Q1 and Q2 the terminals both read Collector, Base, Emitter from top to bottom.

[GibsonGM]

Uh on...you need to go back thru your SCHEMATIC, and be sure all your connections are right!    That hot battery means something is shorted out - could be as simple as some solder creating a bridge between 2 pads that shouldn't connect, or a piece of vero not cut all the way.     It's not as bad as it sounds - get busy!  Hope you figure it out! )

[tommycataus]

Thanks

I've checked it all again, every connection. I replaced the two 0.22uf caps with electrolytics as leads 2 and 3 (to the pot lugs) were showing 0V. I've since sorted the issue and the gain sounds a little low, but I'll do more tweaking tomorrow as it's late.

Oh, and guess what the squealing was?

...

I put the jack leads in the wrong way around! Never had that happen with any wah I've used before but I'll not be making that mistake again in a hurry 

Thanks for your help, I'll keep you posted.

P.S. I just noticed the comment on the PCB layout that says "not to be posted on any other site"... have I violated any forun/general rules by doing that? If so I humbly apologise.

Tom

[tommycataus]

 

Design is now working! Much thanks as I've been reading around this site an awful lot, hopefully some might enjoy building this circuit in future as it's vero-verified.

*I used a Whipple inductor and 100K ICAR pot courtesy of a certain well-known vendor
*All caps (except the 4.7uf) have been changed back to poly
*Tranny terminals are C, B, E from top to bottom
*Wah in parallel to the inductor is now 68K, sounds fuller
*1.5K resistor is now 2.2K to account for mid-range
*470R resistor is now 330R to give a greater bass response (I may also alter the sweep cap to a slightly higher value)

I've also built it into an old ColorSound Wah + Swell enclosure I found that had been gutted and rescued. I prefer the mechanism to the more standard "rack and pinion" style as it feels more sturdy.

[tommycataus]

http://www.youtube.com/watch?v=h_1-fgcHPsc&feature=youtu.be

[joegagan]

sounds great! it has a nice wide range, and a vocal wow sound.

you can use the youtube button on the message window to embed vids:

[tommycataus]

Thanks Joe, thanks for the tip too