#1
So I decided to do the vocal, mid boost and range change mods to my '92 GCB-95. I did all three at once, so it sounded way better than before and couldn't notice any problem, other than the vocal mod didn't seem to make much of a difference.

Yesterday, I decided to replace both resistances (the 68K I used for the vocal mod and the 2K I used for the mid boost) with pots to be able to tune it to my liking. Immediately after I finished I gave it a try. The low-mid boost pot (a 5K) worked flawlessly, but the 100K pot I used for the vocal mod didn't seem to affect the sound at all. I read its resistance with a multitester and it marked around 15 Ohms, no matter what position I turned it to.

Of course, the first thing I thought was that the pot was shorted, so I took it out. For some reason I decided to test it again, and now the damned thing was working fine. Then it hit me: it could be the wah circuit itself that was having the problem! I tested the resistance between the leads that went to the 100K pot and there it was, 15 Ohms again instead of "infinite". I compared the sound I got by just leaving the leads with no resistor and putting a spare 68K between them, and it sounded the same. Just joining the leads together would change the sound, but it wasn't nice at all.

After that test, my guess is that there's a short somewhere in the circuit. That would explain the very little resistance between the leads (the short would be that 15 Ohm resistor), why putting a resistor between them doesn't affect the sound (a very large resistor in parallel with a very small one results in a value very close to the smaller one) and why it WOULD change by just joining the leads (that would basically "short the short"). Oddly enought, it's been that way ever since I bought it. The thing is, I don't know anything about wahs (what if that is completely normal, and the problem lies elsewhere?), or circuits of its kind, to know if I'm right or what to do about it.

tl;dr version:
My wah seems to have a short that bypasses the vocal mod resistor. I don't know if that's normal or where to start to get it fixed. A little help, pretty please?
#2
after readng that wall of test, i understand almost nothing but i figured out we both have a GCB-95. mine works fine.

sorry
Gear

Guitars
Ibanez ART 300
Squier Strat
Godin 12 string Antique cedarburst
Ibanez RGD 320

Amps
Peavey Vypyr Tube 60W
Peavey Solo 15 W
Fender 10 W

Effects
Dunlop GCB - 95 Crybaby wah
Boss DD-7 Digital Delay
Boss MT-2 Distortion
#3
Well, if you haven't modded it you won't understand a thing. It's much easier than I make it sound, just desoldering some stuff and replacing it with other. Or at least that's how it should be, there's something wrong with mine. Hopefully someone who modded his pedal and knows what I'm talking about will read this.

EDIT: Just in case, these are the instructions I followed. I skipped the true bypass and went straight to the tone mods.
Last edited by The_Bozz at Aug 7, 2009,
#4
The mid resistor, inductor, and 33k resistor(in your case 100k pot) all have to go thru a cap. The sweep cap is gonna cause all sorts of problems if you try to do ohms reading. Plus there is a 4.7uf cap and 82k resister going to ground off one side of the resistor/inductor. All that stuff in there is gonna give you funky ohms readings. I did the vocal mod to mine and its not like its some monumental change its very subtle. The mid boost will kinda jump out at you.
#5
Quote by Tackleberry
The mid resistor, inductor, and 33k resistor(in your case 100k pot) all have to go thru a cap. The sweep cap is gonna cause all sorts of problems if you try to do ohms reading. Plus there is a 4.7uf cap and 82k resister going to ground off one side of the resistor/inductor. All that stuff in there is gonna give you funky ohms readings. I did the vocal mod to mine and its not like its some monumental change its very subtle. The mid boost will kinda jump out at you.


Haha yeah, the middle boost was incredibly notorious, having it through a pot is neat. What a shame about the vocal mod, tho. Because of all the comments about it, I thought it would make a big difference and I can't hear it at all (if I'm wrong and the board isn't shorting, but I don't think it's shorting because I just can't find anything that seems wrong). Well, I busted the 100K pot trying to find out what the "problem" was, and I have to ride the bus and take the subway like 1 hour just to get to the closest electronics store

BUT, I still have a variable capacitor left to install. I also did the "lower range" mod in that page, changing it to a "variable range" mod should be fun