HELP WITH GGG MOD-WAH PROJECT

[Govmnt_Lacky]

Finished building the ggg mod-wah and I have a couple issues:

1) I built the PCB to spec according to JDs site. I used a RED Fasel and a YELLOW Fasel for my inductors. The problem I am having is that when I have the RED Fasel selected, the wah sounds fantastic with no issues at all. However, when I flip the switch to the YELLOW Fasel, I get NO WAH sound at all! Only the regular audio.
Both inductors came from Dunlop and I assume they are good.
My question(s) are.... Do I need to adjust any of the trim pots (the Q especially) when I switch between inductors? or
Are there any ways to check the YELLOW Fasel to see if it is indeed GOOD???

2) The build text file says to put a 1M resistor on every lug of the rotary switch to prevent "popping" when switching between caps. My question is:
Can I just put (1) 1M resistor on the input of the rotary switch INSTEAD of putting one on every output lug? Will this prevent the popping?


Thanks to all who respond for your help.......

[R.G.]

1) ..., when I flip the switch to the YELLOW Fasel, I get NO WAH sound at all! Only the regular audio. Both inductors came from Dunlop and I assume they are good.
My question(s) are.... Do I need to adjust any of the trim pots (the Q especially) when I switch between inductors?

In general, no, a pot trim change is not needed to hear a wah effect. It might be needed to get best results to a fussy ear, but not just to hear wah-ing.

or Are there any ways to check the YELLOW Fasel to see if it is indeed GOOD???

There are ways, yes, but they require equipment that you may not have. Measuring the resistance from end to end is about the only thing you can do with a multimeter. IF it's open, resistance over a few hundred ohms, then it is definitely dead. But there are ways for it to pass this test and still be bad.

I'm not familiar with the PCB, but it's more likely that wiring and soldering issues are the problem than the inductor. Can you swap it into the position where the Red inductor is, to eliminate PCB problems? Perhaps put the known-good Red one where the suspect Yellow one is? That would tell you if it's the inductor or the position on the board. If neither or both of them work after this, it's likely to be soldering/wiring. Parts can be bad when new, but it's vastly more likely to be assembly problems.

2) The build text file says to put a 1M resistor on every lug of the rotary switch to prevent "popping" when switching between caps. My question is:
Can I just put (1) 1M resistor on the input of the rotary switch INSTEAD of putting one on every output lug?

Yes you can, but...

Will this prevent the popping?

No, it won't. The whole point of the pulldown resistors is to hold the open ends of the caps at a fixed voltage so their ever-so-slight leakage will not change their DC votlage and then cause a pop when the switch is changed. For that, the resistors all need to be on the un-connected ends of the caps.

[Paul Marossy]

Check for continuity on your yellow Fasel. If there is a broken wire inside of it or at the pins where you solder to it, it will do nothing. I've had at least one bad inductor due to that over the years. And also check to see if it really is in your circuit when you switch in "on". Maybe the PCB has a defect or something...

[Govmnt_Lacky]

First of all, let me put a link on here for the layout that I built from:

http://www.generalguitargadgets.com/diagrams/wah_mod_lo_1_toggle.gif

Now, after reading the first two replies I did some debugging. It was simple actually at least the way I thought.

I read resistance through both Fasel inductors. The Red one reads 15.5 ohms. The Yellow one read 22.5 ohms. (The inductors were read while on the PCB however, I was able to isolate them by selecting the DPDT toggle to the opposite inductor I was metering at the time.)
Next, I read the resistance through the DPDT when the inductor WAS selected. The Red, when selected, measured 16 ohms. The Yellow, when selected, measured 23 ohms.

So.... it appears that the selected inductor IS IN FACT in the circuit when selected by the DPDT.

One tid bit. The Yellow Fasel plastic cover comes off easily so I used some small tape strips to keep it on. Dont really see how this would be a player but I thought I would mention it.

Any other ideas on what may be causing my problem??

[Paul Marossy]

Hmm... the only reason I can think of for it behaving that way is that your yellow Fasel is somehow being defeated and not actually functioning in the circuit. Are you positive that the wiring on the DPDT switch is correct? Maybe you transposed a wire?

[Govmnt_Lacky]

Just finished doing a visual on the pedal and compared it to the layout in my previous post. The wiring from the inductors to the DPDT is IDENTICAL. It also meters out good.

I am officially STUMPED!!!!!!

Any other ideas??? Starting to look at a possible bad Yellow Fasel but it measures good resistance!!!?

[Paul Marossy]

I don't think that it's the inductor itself. If it was, you shouldn't be getting any resistance measurements as it would be an open circuit.

If it's wired correctly, and there is no mistake(s) on that GGG PCB layout, then it should be working....

[Govmnt_Lacky]

Paul,

It has actually been a while since I fired up the Mod-Wah and played through it. I will plug it in later today and give it another listen then report my findings here. Maybe by describing the sounds that it is making might help. It may very well BE working but I just dont hear/feel it. I know when the RED is selected I get a SWEET wah out of it though.

I will post later when I get it fired up.

Thanks for all your help so far..... Stay Tuned!

[Paul Marossy]

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