Dunlop Wah Volume Problems after Mod

nephsuperman · January 10, 2007, 10:18:49 AM

I have done some modifications as specified by this site:
http://www.stinkfoot.se/andreas/diy/mods/dunlop.htm#RevE
I did the buffer removal, scratched the connection between the input jack and the buffer, and added the output wire and ground wire to the PCB. I also changed out the factory switch with a true bypass switch. Additionally I also changed two resistors because I had a lot of volume loss. I changed the 68K input resistor to a 47K and I changed 33K resistor to a 56K. as shown in his diagram.

My problem is that there is still tremendous volume loss even when its rocked back towards me. When it is rocked back to the switch end, there is almost no sound at all. To me it really sounds like a volume pedal right now, and I don't want a volume pedal. The true bypass is sweet, but I want my wah wah back. The What am I to do?

Here is my wah. I highlighted the resistors that I changed. Thanks in advance!

O · January 10, 2007, 10:22:46 AM

There are different mods for the different board revisions. Did you use the right one?

nephsuperman · January 10, 2007, 10:25:37 AM

Yep, I believe I have an E because on the bottom right, there is a big E printed on to the board, but I may be wrong.

jonathan perez · January 10, 2007, 10:36:01 AM

maybe your electrolytic is blown...put your meter across the 4.7uF electrolytic capacitor, to see if its still good for go...every dunlop repair has the same problem, in that the electrolytic is dead...

nephsuperman · January 10, 2007, 10:40:32 AM

I will check the electrolytic, I am still fairly knew to this whole game, how do I check it with the multimeter to see if it is blown, or functional? I know its a stupid question, but I have to start somewhere.

Beyond that, if that isn't the problem, what else should I be looking for?

jonathan perez · January 10, 2007, 10:49:37 AM

well, if you want to go simple, just replace it and see if that works.

beyond that, make sure that you cut the right trace...otherwise you may find yourself having to use a jumper...

nephsuperman · January 10, 2007, 09:00:18 PM

Added the 4.7uF electrolytic and it did the trick in terms of the wah sound, the wah sound is back. But the volume is still really, really, low compared to when the bypass is on. again rocked back all the way towards me is loud and all the way towards the switch is almost unhearable. I do not know what to do for this, could someone please help? Should I add the buffer back?

Thanks.

tcobretti · January 10, 2007, 09:15:38 PM

I would check all of the new solder joints; those Dunlop boards are easy to damage when soldering.

nephsuperman · January 10, 2007, 09:29:55 PM

Nope, those have all been quintuple checked, it aint those. any other ideas?

nephsuperman · January 10, 2007, 10:23:34 PM

Could it possibly be the other electrolytic in the board, the 220uF? Otherwise could it be the inductor? Do i have to turn the inductor to change the volume, or could it be busted and result in this crazy volume change?

jonathan perez · January 10, 2007, 10:26:48 PM

honestly, i usually leave the buffer alone, i think it sounds fine in the new wahs. its the OLD wahs, sans buffer, that sound like shit...

if its a case of volume, whats your rig lookin like?

nephsuperman · January 10, 2007, 10:48:10 PM

for testing purposes, i am just running it from the guitar to the wah to the amp. that is it. when its bypassed, i get normal levels, when its on, its tremendously lower. I am going to put the buffer back in.

jonathan perez · January 10, 2007, 10:50:09 PM

try a 33k volume resistor.

jonathan perez · January 10, 2007, 10:51:53 PM

also, are you sure that 56k resistor is a 56k, and not 56 ohm? i cant tell.

nephsuperman · January 10, 2007, 11:05:29 PM

its green, blue, orange, which is 56K.

zarathustra · January 10, 2007, 11:05:52 PM

I did a bunch of these mods a few weeks ago. One thing I noticed is that, in addition to the input resistor, the capacitor next to the emitter of Q1 (it's the one labeled 390R with the red arrow in your photo) has a substantial effect on your gain levels. You might want to try putting a 300R or lower cap in there. (You'll also get more bass response with a smaller cap, which may or may not be desirable for you.)

Also, are you sure it was necessary to cut the trace? When I modded mine (it's a GCB95, though I don't recall which version) I had the option of either leaving the buffer intact and cutting a trace OR removing the buffer completely and leaving all traces uncut.

jonathan perez · January 10, 2007, 11:40:47 PM

Quote from: zarathustra on January 10, 2007, 11:05:52 PM
Also, are you sure it was necessary to cut the trace? When I modded mine (it's a GCB95, though I don't recall which version) I had the option of either leaving the buffer intact and cutting a trace OR removing the buffer completely and leaving all traces uncut.

and does not cutting the trace work fine? no volume loss?

tcobretti · January 11, 2007, 02:10:55 AM

I just realized that revision E does not have the buffer, so you have F,G, or H. My understanding is that you didn't need to cut that trace IF you remove the buffer components, but that is not likely the problem unless you cut the wrong trace.

Because the problem is only when you rock the pedal forward, logic dictates that either you wired the pot/switch wrong, or something is wrong with Q2 which generates the sounds you hear with the pedal rocked toward the toe. If you didn't change any other components beside the ones you listed, I think Q2 failing is somewhat unlikely. Looking at your pic, the blue wires look weird in the one pic we have of them. Remember, one blue wire goes from the PCB to lug 3 of the pot, then the other goes from lug 3 to the switch. I suspect that the inductor is ok because it does wah a little. The 220u cap is for power filtration when you are using a power supply, so you could take it out; however, if you didn't solder on it at all it is very unlikely that it is the problem.

I personally would not bother messing with the buffer, the 390r resistor, or the 47k input resistor because the pedal works fine (right?) in the toe up position. If these guys were the problem I'm pretty sure you'd have different symptoms.

What I don't understand is how did the 4.7u cap go bad? Did you remove it previously for some reason? Did you swap any components besides the ones you listed?

zarathustra · January 11, 2007, 02:34:34 AM

Quote from: thebattleofmidway on January 10, 2007, 11:40:47 PMand does not cutting the trace work fine? no volume loss?

Minimal volume loss, if any, although I did drop the 68k input resistor down to a 47k just for the hell of it (and now I actually get a bit of a boost from the wah). I definitely didn't encounter the substantial volume loss that nephsuperman is experiencing.

edit: and yeah, like tcobretti said, your blue wires don't look right. There should be two: they should both connect to the same lug on the switch, with one going to the PCB and the other going to the pot. Where's that other blue wire going?

jonathan perez · January 11, 2007, 02:42:25 AM

Quote from: tcobretti on January 11, 2007, 02:10:55 AM
What I don't understand is how did the 4.7u cap go bad? Did you remove it previously for some reason? Did you swap any components besides the ones you listed?

not even i can figure that out....but everytime i get a "broken" wah, its always JUST the 4.7

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Dunlop Wah Volume Problems after Mod