Red/Yellow Fasel pain in my WAH!

[Govmnt_Lacky]

So... I built the modable Wah project from GGG. I decided that I was going to go all out and do the following:

Install a Red and Yellow Fasel on the board.
Used the DPDT toggle to switch between the Fasels.
Installed a 1-pole/6-position rotary to switch between input caps.

I was able to get this all installed and situated in a Dunlop-style Crybaby rig. So.... here is the problem...

When I switch the DPDT to put the Red Fasel in the circuit, this bad boy sounds FANTASTIC! However, when I switch to the Yellow Fasel it BARELY cries.

I know there is a difference in the two inductors however, the yellow BARELY wahs.

Basically, I am asking for any inputs on how to test if I possibly have the following:

1) Bad Yellow Fasel (are there tests that can be done to the Fasel to verify it is good?)
2) Need to make adjustments to any of the trimmers due to inductor changes
2) Are the inductors position sensitive? Do they have a positive and negative polarization and maybe I installed the Yellow backwards.

Could this simply be a matter of adjusting one of the trimpots to find a balance between the two?

[Talon5051]

I did pretty much the same build.  The only test that I can think of for the inductor is to ohm it out and see if it measures the same as the red one.  You may need to remove them from your board.  You could also just have a bad solder joint on the yellow fasel.  There are no adjustments that you need to make nor do the inductors have polarity.  I honestly could not tell the difference between the different inductors but when you put them in series it does make a big difference.  Do you have different caps for the 10nf that connects to the base of Q2?  You mention input caps but is this the cap that you are switching?  Have you tried all of the caps on both inductors?  I accidentally    installed pico fared caps instead of nano fared and it will not wah very much.

[Govmnt_Lacky]

I was assuming that the switchable caps were "input" caps. I am probably wrong however, I did put the suggested values in for c2a through c2f.

I do know that I need to make some adjustemnts to the trimpots because even though it sounds great through the Red Fasel, it still needs a tweak. (has too much treble for my taste and not enough sweep low to high)

I posted this a long time ago but never really got anywhere with it. Might have to break out the old wah and finally get her FULLY working. Here is a link to my older posts:

http://www.diystompboxes.com/smfforum/index.php?topic=73394.0

Any ideas are welcome because, as I recall, this one stumped me pretty good.

[tubelectron]

Hi Govmnt_Lacky,

1) Bad Yellow Fasel (are there tests that can be done to the Fasel to verify it is good?)

You can measure the ohms, as stated, but you should measure the inductance too - there is cheap and correct RLC DMM able to do that. But a bad inductor would be surprising... Anyway, you should find 15 to 30 ohms as a guideline, usually, and if yes, the inductance should be then correct (500 to 700mH usually). Less ohms = short circuit / infinite ohms = coil cut.

2) Need to make adjustments to any of the trimmers due to inductor changes

That may be possible, but it is only adjustment, in order to have better wah operation. If it really doesn't work, chances are that there is a "good old mistake" somewhere... Nonetheless, making a good sounding wah is not so easy (I personnally find all the stock GCB-95 and V847 as treble factories, asking for modification to have smoother and more vocal operation, both for rhythm and lead).

2) Are the inductors position sensitive? Do they have a positive and negative polarization and maybe I installed the Yellow backwards.

In this case, the position of the inductor is not important, because there is no transformer able to induce 60Hz hum in your pedal, which is furthemore a shielded box. There is no polarization for such inductors, so you can wire it in any sense for the same result.

A+!

[Paul Marossy]

I was assuming that the switchable caps were "input" caps. I am probably wrong however, I did put the suggested values in for c2a through c2f.

Those are different sweep cap values. Stock is a 0.01uF cap.

[Govmnt_Lacky]

I guess I am going to have to rip this beast apart and check copper traces and check for solder runs. I wish I was savvy enough to post some sound clips of the different Fasels in use. I am not familiar with how to post sound clips on here.

[deadastronaut]

I guess I am going to have to rip this beast apart and check copper traces and check for solder runs. I wish I was savvy enough to post some sound clips of the different Fasels in use. I am not familiar with how to post sound clips on here.

join dropbox...nice and simple..make your mp3 drop it into your dropbox public  folder on ya pc...right click on the mp3file ,copy public link..

and paste into your message between the url's....sorted. hope this helps!.

rob.

[Govmnt_Lacky]

Well, I opened up my mod-wah and I am right back where I started. I checked for bad solder runs and copper traces and found nothing. I measured the resistance at the DPDT switch with JUST THE YELLOW FASEL in the loop and it measures 22 ohms.
The best way to describe the problem is that when I switch the RED Fasel into the loop, I get a nice deep WWWAAAAHHHH from heel to toe. When I switch in the YELLOW Fasel, I get what sounds like a treble adjustment but, NO WAH AT ALL.
Do I need to just bite the bullet and swap out another Yellow Fasel? I tried adjustments on all of the trimpots to no avail.
Can an Inductor be bad and STILL measure ohmage correctly? Has anyone ever had this problem before?

Any help is appreciated?

[Paul Marossy]

Can an Inductor be bad and STILL measure ohmage correctly? Has anyone ever had this problem before?

The fact that you have continuity between pins on the inductor is a good sign. I've had ones with a broken wire which rendered them useless. It could be that the core is somehow defective, but I've never really heard of that happening before.

Having eliminated all other possibilities, the inductor might be bad. Are you sure that the inductor switch is wired correctly?

[Govmnt_Lacky]

I verified the wiring with the layout on GGG as far as the inductors are concerned. It is all correct. I did get my replacement Yellow Fasel in the mail and the only difference is that the one installed measures 23 ohms and the "new" one measures 17 ohms.

I guess I will just have to bite the bullet and replace the Yellow.

I also triple checked for solder runs and usedd the DMM on the DPDT switch. All looks good. All things are pointing towards a bad Fasel.

I will replace it this weekend and post results.

[Paul Marossy]

It kind of sounds like your yellow Fasel may not actually be in the circuit. Are you sure that it's plugged into the right place on the PCB?

[tiges_ tendres]

Why not eliminate the switching of the inductors all together.  Set the wah up with the yellow fasel only, no switch no funny business.  Then let us know how that goes.

[Paul Marossy]

Why not eliminate the switching of the inductors all together.  Set the wah up with the yellow fasel only, no switch no funny business.  Then let us know how that goes.

Yeah, good idea.

[Govmnt_Lacky]

It kind of sounds like your yellow Fasel may not actually be in the circuit. Are you sure that it's plugged into the right place on the PCB?

Yes. The Yellow is installed in the correct spot and it is wired properly to the switch.

[Paul Marossy]

Did you buy a PCB from GGG or etch one yourself?

[Govmnt_Lacky]

Did you buy a PCB from GGG or etch one yourself?

I etched the PCB myself based on the GGG design (Thanks JD!!)

I replaced the Yellow Fasel today and got to hook up the rig to a signal generator and oscope. According to the oscope, with 440Hz at 100mV, both Fasels appear to be doing almost the same thing. I posted another thread on here asking about what to look for on my oscope. The link is below.

http://www.diystompboxes.com/smfforum/index.php?topic=86559.msg725214;topicseen#msg725214

[Paul Marossy]

That's weird. I have used both types, and there really isn't that big of a difference between the two. You should be hearing a wah effect with your yellow one, too.

[Govmnt_Lacky]

Paul,

I agree. Like I said above, I replaced the Yellow with a new one today. I ran it through my bench set up (signal gen and oscope) and the signal looked about the same with the Yellow or Red Fasels in the loop. I just wish I could find a link to an oscope screen shot of what a wah looks like through the spectrum. (i.e. from heel down through toe down)

Basically, as I ran the 440Hz/100mV signal through, at full heel down the signal was at about 50mV. At mid point in the sweep, the signal amplitude got up to about 1kHz. At full toe down, the signal amplitude went back down to about 75-50Hz. I dont know if this is good, bad, tuned right, etc.. That is why I would like a reference. The frequency did not change...only the signal amplitude. I think that is right. 

[Paul Marossy]

The function of the inductor in the wah circuit is simply to make it a resonant circuit. It doesn't make sense to me that one inductor would work and the other one doesn't unless there is a mistake on the PCB or something is wired incorrectly which essentially takes the yellow one out of circuit.

What happens if you take the red one and put it in place of the yellow one and vice versa?

[Govmnt_Lacky]

Paul,

Well, I put a brand new Yellow in place of the suspected bad yellow. I will try it tonight and post back tomorrow. I verified all wiring, copper traces and switch functionality. All of that stuff was good. Everything points towards that Yellow Fasel being bad somehow. I thought that maybe it could have been a bad/cold solder joint at one of the Yellow Fasel legs however, it read ohmage between points on the DPDT switch when it was isolated.