Wah Pedal Building... circuitry 101... help...

[njschenck]

So, I've decided to build my own wah pedal.  Actually, my friend was brave enough to hand his over to me after I modded mine and said, "do that to mine."  Of course, he had one of those crappy Dunlop Q535's, which had a computer chip in it, basically - so I've had to start from scratch.  Well, I got my hands on it and there's now an all-original pcb (designed myself from a VOX schematic with the few mods I made on my own pedal).

Everything looks right, and seems like it should work when wired up, but, as you might have guessed by my posting, it has all but worked. 

I've checked everything - the multimeter shows connections where there should be, but there's no signal getting through the board.  I'm so frickin' confused, and slightly annoyed; I've built a flashy, rocking bypass switch that lights up when you engage it.  Suggestions anyone?

[rockgardenlove]

Got shematics/pictures?

[LP Hovercraft]

http://www.diystompboxes.com/pedals/debug.html  The audio probe is a very nifty little device that will tell you how far into the circuit the signal is actually going. 

[njschenck]

Hey, the audio probe thing sounds like a great idea - I'm trying that one lter today.  As for pics/schematics, I'd show you if I knew how to post pictures... sorry.  Kinda new at this; if you tell me how I'll have them up for your evaluation.  Thanks.

[Paul Marossy]

Hey, the audio probe thing sounds like a great idea

Well worth the time and effort to make it! It's saved my bacon many times. 

[AL]

Another vote for the audio probe. Most useful build I have done and it has saved me countless hours of debug time.

You didn't really give enough info for anyone to pin-point a specific area so definitely build the probe and work your way through the circuit. You should have it up and running in no time.

AL

[njschenck]

I'm new to this whole forum thing - I've grown desperate and frustrated and need help.  If you can explain the process of loading a picture (as simple as it seems, it completely eludes me), I can have pictures of the schematics I used, the board I designed, the board I assembled and the mess-that-is-the-wah-I-built.  Thanks, all.

[Paul Marossy]

If you can explain the process of loading a picture (as simple as it seems, it completely eludes me)

You have to upload it to a server and then link to that server. If you don't have your own domain to load it to, you can upload it to something like photobucket, which I believe is free.

[formerMember1]

Check to make sure nothing is grounding to the wah shell.  For some reason, everytime i build a wah and it doesn't work, a resistor lead isn't clipped off enough and it touches the mounting post...   to check, measure continuity between power and ground  if there is continuity, you have a short...

measure your transistors and see if they are getting power...
if not
probably a wiring error...  What diagram/bypassing arrangement did you use?

You said you made your own board from a wah schematic,.. check over to see if the scheme matches your board layout...

also can check to make sure you actually ahve the pinout of your transistors correct, and make sure your resistors are indeed the correct value and not a 8.2k instead of 82K or something...

i always mix up the 47K with the 470K or something like that...

here is  a resistor calculator to check your resistors in your wah,.. 
http://www.ealnet.com/m-eal/resistor/resistor.htm
there is a better one around, but can't find the link...

also be sure to search the forum for wah tips/mods,.. there are many many ideas and things to try on here...

[formerMember1]

BTW, Welcome to the Friendliest Forum 

[njschenck]

Thank you much - I appreciate all the help/tips.  The photobucket thing, by the way, is great. 

The resolution isn't great, and I apologize for the poor photographs, but it's my boss' camera and I'm not too familiar with it.  There's a pic of the board with everything mounted, the wiring of the switch, and the underside of the board.  My fear is that you'll look at it and laugh at the elementary approach I've taken (without my  meaning to), but I need some direction...

I'll also link to a copy of the schematic (sans mods I've made to a few of the resistors), and a copy of my layout.  Thanks again, and again.

http://i72.photobucket.com/albums/i196/njschenck/wah1.gif
http://i72.photobucket.com/albums/i196/njschenck/WahCircuit2.jpg
http://i72.photobucket.com/albums/i196/njschenck/IMG_2367.jpg
http://i72.photobucket.com/albums/i196/njschenck/IMG_2363.jpg
http://i72.photobucket.com/albums/i196/njschenck/IMG_2362.jpg

[formerMember1]

I can't tell by the board side pic, but it looks like there may be a few bad solder joints, or solder joints that are touching another joint that it shouldn't.

There also seems to be more wire then there should be?  MAybe  a wiring error....

post your transistor voltages and maybe someone can help from there....