Debugging my "Seek Wah" with solderman wah board

[ugly_guitar_guy]

Hey guys,

So I've been working on my seek wah-type effect for a few years now and finally have the motivation to finish it. I followed the directions that I found here: http://www.allaboutcircuits.com/vol_6/chpt_7/6.html to learn how to make a sequencer since my attempt at the Vanishing Point failed miserably, and now have a nicely working sequence section. See my video here: http://youtu.be/n5hyh8qRd_M

I then found Soldeman's "Hide and Seek" build (http://solderman.fatabur.se/Future%20project/Lost%20Wha.pdf) and decided that I liked the way his sounded, and it was also tested to work. Well, tonight I got my sequencer board linked up with my Solderman wah board using a VTL5C9 Vactrol, and plugged in. The sound is very quiet, and not "wah filtered" or following anything from the sequencing board. It sounds pretty much just like a quiet guitar signal.

All of the components on the board are the same as in Solderman's layout except for the 2N5088 transistor, which I used an NTE 123AP because that's what I could get here (and the guy told me it was a sub). This is my first "debugging" attempt and I'm not even sure if I used the multi-meter correctly to get these numbers, so please bear with me. The readouts were as follows:

C: 7.78
B: .58
E: 0

Also, here as the pics of my board next to solderman's layout in the pdf:

top:


bottom:



Thanks guys, this build is slightly over my head and your help is mightily appreciated!!

[blooze_man]

The trace connecting R1 to R10 is missing.

[ugly_guitar_guy]

The trace connecting R1 to R10 is missing.

blooze man, you are correct. I'll get that fixed and report back!

[ugly_guitar_guy]

So hypothetically, if that missing trace is the "problem" here, I should be able to wire up power and jacks and get SOME sort of filtered sound, or does something have to be connected where the LDR goes to make that happen? I just want to test the audio circuit before wiring it up to the sequencer.

Thanks!

[arma61]

or does something have to be connected where the LDR goes to make that happen?

I think, being that the LED/LDR combo form a sort of variable resistor, you need a pot there, turning it you should hear the tipical wah effect

[ugly_guitar_guy]

or does something have to be connected where the LDR goes to make that happen?

I think, being that the LED/LDR combo form a sort of variable resistor, you need a pot there, turning it you should hear the tipical wah effect

Any idea how I should wire that up? Would I wire up pins 1 and 2 to ground and 3 to the circuit?? I have an extra 1M pot sitting around so I guess can plug that in and see what happens.

[arma61]

yes, that's it

look at this

http://www.diyguitarist.com/PDF_Files/ColorsoundWahPCB.pdf

[ugly_guitar_guy]

Ok, I wired in that missing trace, and fired it up. I get normal volume level now, but the filter effect is only very slight. It sounds like rolling back the tone knob on the guitar like 1/3 of the way. I tested the trans and got exactly the same numbers that I already posted. Any other thoughts?

[ugly_guitar_guy]

anybody?? I'd really like to try to get this wrapped up this weekend...

[ugly_guitar_guy]

ok, so after not getting the solderman circuit to make any kind of wah effect I decided to make the colorsound wah circuit from the layout that arma61 posted above, and that barely makes any kind of filter effect at all when I sweep the pot and cuts the signal gain by probably about 40%. Im getting frustrated with how simple this should be and I can't even get the basic wah circuit to work. I could really use some help...

[arma61]

Hi, the only thing that comes to my mind is about the sub of the transistor, are you sure they are equivalent ? have you checked the datasheet, could be the pins are different? or the hfe ?

I cannot find anymore my circuit to make some measurement, (I'm quite messy!  ) , I'll have a search again this morning!

[arma61]

Hi

I've found it! Readings looks almos like yours

C 6.98
B .63
E 0

have you tried with an audio proble to tace the signal and find where it  "get lost" ?

[ugly_guitar_guy]

well, everything is getting through after another thorough circuit check and audio probe. Are the type of caps that I use important? I'm just using NTE ceramic caps from my local electronics store. How much "wah" should I be getting from the circuit when I turn the pot?

[ugly_guitar_guy]

UPDATE: Ok, so I this was my first time using the audio probe and I was doing it wrong. Got it figured out, and I get full sound until after the 330k resistor and then it gets very quiet, then following the signal path it gets quieter and quieter until the guitar is like half the gain at the output. Thoughts?...

[arma61]

suspect you've something weird with your transistor, either wrong pins orientation or components in the neighbourhood.

About caps providing the value is the same, type is not important just to let it working, then, once it's working, you can choose your preferred ones

[ugly_guitar_guy]

does it make a difference if I use caps rated in pF instead of uF? For instance, I used 15000pf caps where it says to use .015uF. That should be a correct substitution, right?

[arma61]

yes, you're right, same value.

[ugly_guitar_guy]

then I'm not sure what to do to fix the board and get it working right. I've traced and retraced and re-retraced the layout, checked my components, checked the transistor, used the audio probe (but I don't really know electronics well enough to know if I'm finding a problem or not) and I'm still coming up empty handed. I guess my next step is to try and etch a board instead of doing it on perfboard.

I can't believe that I can't get this one stupid little circuit to work....

[arma61]

hi

Just remember now it sounded better with a Tillman preamp (or any kind of boost) in front of it. I've re-tested now, and  without the boost it's really subtle, though definitively, you should hear a wah effect at the junction R3/R2/C5/C3 (on solderman schematic), at least I have it on my board.

Sorry I can't help you very much, but at this stage I think the best way is to redo it, it's so little components count, better if you have a breadboard to play with!

[ugly_guitar_guy]

first armando, thanks for all your help! it's been hugely appreciated.

second, through a search I just found a schematic for the colorsound wah over at beavis audio (http://www.beavisaudio.com/Projects/ColorsoundWah/index.htm), and it appears that both the .01uF caps located at the input and output should be .1uF, not like what is on the "diyguitarist" layout. could this be the source of my troubles since all other values appear to be the same?