Wah Problem - No Bypass Signal or Wah Signal

[nation]

Hi All

Hope I can get some help on this. I get no bypass signal or wah signal with true bypass wiring. Is my PCB damaged?

I have a Vox wah and have replaced the PCB with an Area 51 PCB. The PCB has been wired true bypass with LED and I have done the following the mods to the circuit; buffer circuit (connected via the green wires to the red on/off switch in the pics), rotary switch for the voicing, pot for wah sweep and pot for gain. The wah has been working perfectly like this for a couple of years. Last week I decided to experiment with cap values for the voicing switch, changed out a few few values and testing was going well. A few cap changes in and my wah suddenly stopped working -  no bypass signal, no wah signal. At first I thought a wire may be have come loose but after searching nothing came up. I have since spent the last few days trying to solve this problem, changed the switch, changed the jack, gutted and rewired the wah a number of times, tried different methods of true bypass wiring etc. all with no success.

The first diagram below is my original off board wiring when the problem first arose. Like I said it was sudden, all was working well, I changed a cap, turned the wah right side up and had no bypass or wah signal.  The other pictures are the current state of my wiring.

When I plug in guitar cables to the input and output jacks I noticed the tips and the shields of my input and output cable seem to be connected i.e. my multimeter beeps if I touch the shield of the input and tip of the output. My 3DPDT switch also connects all 6 points on the 2 wired poles, the unwired LED pole works as expected.

Could there be a problem with my PCB or is this a wiring fault? Any help on this would be great.

[lukeferg]

Hi mate,

Having no resistance between tip and sleeve is your issue. You're pcb is probably fine.
I would be checking all your ground connections including backs of pots, jacks etc. Somewhere you've got a short between input and ground.
Just to clarify, you're getting no resistance between tip and sleeve. Is that with the pedal bypassed and non-bypassed? If there's no resistance all the time then I would be looking at your input and output jacks as well as your switch. Sometimes wires aren't connected but they look ok too.
I use the tonepad wiring, works every time.
http://www.tonepad.com/project.asp?id=35

Good luck

[nation]

Thanks Luke. I figured it has to be a ground issue somewhere. Just to clarify, when I touch my multimeter on the cables my multimeter beeps whether I'm touching tip to tip, sleeve to sleeve or tip to sleeve. Could it be that my jacks are ground out on the wah enclosure? I get no connection when I remove the input and output jack from the enclosure. I did notice at one point in my testing that when I loosened the jacks and jiggled them around in their holes I was able to get a signal but that came with horrendous background noise. I have been over this a number of times and just can't work out the problem hence why I m wondering the problem may the grounding pad on my PCB?? I'm stumped that when the problem arose the bypass signal just stopped after I changed a cap yet when I checked all the wiring nothing was amiss.

[GibsonGM]

You might try doing the continuity test on your battery clip!   Plug your cables in, no battery...then test between + and - with your 'beeper'.   If nothing....then try measuring resistance and note the "ohms" you get.     This will tell you if you have a short in your power supply.

[nation]

You might try doing the continuity test on your battery clip!   Plug your cables in, no battery...then test between + and - with your 'beeper'.   If nothing....then try measuring resistance and note the "ohms" you get.     This will tell you if you have a short in your power supply.

Thanks, I just tried this and I get continuity beeps and 0 ohms between +ve and -ve of the power supply.

I also made an error in what I said earlier re the cable continuity beeps. I just checked again and I get beeping when touching the input sleeve/output sleeve and input tip/output sleeve.  I get no beeping when I touch the input tip/output tip and the input sleeve/output tip.

[lukeferg]

So your output grounds are connected. They're going to be grounded through the metal enclosure so that's not surprising. But your output tip isn't connected to anything. Check the output tip wire coming from your switch. Use your multimeter and check to see if you're getting signal between the output tip and the switch.
The battery grounding adds another layer to this. I don't like the look of the soldering on your PS board. Check for any solder bridges by running a Stanley knife around and between the pads, maybe reflow the solder on those too. Am I right that you don't have a battery clip?
I'm getting confused with all the different switch wirings you've got. I would rewire the switch according to the tonepad layout I posted. See if that helps, it will at least give you a very standard wiring setup that most people can troubleshoot.
What happens with continuity between input/output jacks when you push the switch? Does it change or stay the same?

[GibsonGM]

^  What Luke said. Also - be sure your cords are good, LOL...I have seen occasions where the CABLE is broken/shorting...doubt that's your problem, but we need to be sure, just something to think about for 1/10th second.

Odds are 1,000 : 1 that something is simply shorting, IMHO.

[nation]

Many thanks for your help on this. I've gone through your suggestions and the problem persists.

Luke - I checked the switch to the output and am getting continuity. Yes you are correct, I have don't use batteries so have not included a battery clip. I have cleaned up the PS board, wicked off the excess solder, reflowed solder onto the contacts and cut between the pads. Plugging in a power cable in I get 9.5V at the PS board. I also just rewired the pedal according to tonepad and rechecked the foot switch which is in working order (I removed the buffer circuit and replaced the voice switch with a fixed cap to take those out of the equation, I left in my pots for the gain and the wah sweep for now). The positive sign is the wah board seems to be working, I can hear it hissing away and can hear the wah pitch change as I move the pedal. Other than that I'm still not getting any signal. It's the same as previously; I get beeping when touching the input sleeve/output sleeve and input tip/output sleeve and get no beeping when I touch the input tip/output tip and the input sleeve/output tip. When I press the switch I get continuity beeps across all points, tip to tip, tip to sleeve, sleeve to sleeve. This is the same behavior as before the tonepad wiring for the switch in either the on or the off position (in my previous post I mistakenly only tested the switch in just the bypass position).

Gibson - I hear where you're coming from, I'm always weary of my DIY cables so the cables are my go to for such troubles.

Do you guys think the problem could be the ground pad on the wah PCB? And if yes, how would I go about checking this? Failing that as GibsonGM said I just got to find this short.

Thanks again.

[GibsonGM]

I would find a way to jumper your guitar to the board input, and amp to the output, to assure yourself that the PCB actually works.  From the SOUND of it, it may (changes in pitch etc...) be fine....I am suspicious of the switch/switch wiring.   This means taking the footswitch out.

If you remove the 3PDT and check that everything is OK just "hotwired", THEN you can start from a known position.  That is just what I would do.   PCB ground to the shell, with the power supply ground.

I think that "something you've done" has caused your signal to be grounded.  It is easy to do this across 3PDT terminals, etc....that's my 2 cents!

If it works without the switch, bam, you know what is up.

[Govmnt_Lacky]

Looking at your "recent" wiring, when the 3PDT is in one of the positions your Orange wire is GROUNDED.

Is this the way it's supposed to be?

[lukeferg]

Any chance we could get a pic of the underside of the PCB? That might help to at least rule out any problems there. I doubt that is your problem but it can't hurt to check.
Also, new pics of the whole pedal after the tonepad rewire will help.
The orange wire is grounding the input when bypassed so I don't think that's your issue either.

The main reason I don't think it's pcb is because it affects the pedal in bypass. Since most true bypass wiring diagrams ground the input on bypass a dodgy ground pad shouldn't affect your bypassed signal.
Have you had a look at your buffer board? Since that affects both on and bypassed signals something may have shorted out there. Test your connections from your buffer switch to and from your inputs and outputs too. A pic of the buffer board wold help too. Do you get bypassed signal when you flick your buffer switch?
Tracing your wiring, I can't see any immediately obvious problem that would be affecting bypassed signal.

[nation]

I finally got it working. My carelessness knows no bounds, I'd imagine the problem was bad tinning of wires as I had a wire which was hanging from it's last strand. I rewired the pedal again using the tonepad method and I am now getting signal.

I really appreciate your help Luke and GibsonGM, just hope I didn't waste too much of your on this.

Thanks again 

[GibsonGM]

Glad it works, Nation, no waste of time!  It takes some doing to learn de-bugging...you just learned a valuable lesson    Look forward to seeing what other things you build and/or invent!