Fix a Wah

[Gargaman]

Hello all
I got this wah (crybaby gcb-95) to fix, seems like it has been modified to truebypass.
The switch is bad; looks weird to me, but apparently is a dpdt diagram.
I'm about to put a conventional dpdt in place.
Any tips?
tks

[Rob Strand]

This article spells out a lot of stuff,
https://stinkfoot.se/archives/546

[Gargaman]

Thank you very much Rob.
Made things really easier.
After reading it's obvious the red wire is part of the mod.
The buffer part is there and looks like it has been through Step 2b.
I won't remove the pcb. Since the pedal was working before the switch breaked I assume the mod has been done good.
The wiring diagram looks like this:


My question is:
Will be ok to apply the DPDT wiring suggested in the article?


If so, the 2 blue wires (one coming from board, another coming from pot) may connect together to 'circuit out' pin, right?
I may find a ground point. Is the black wire on the pot a ground path?
tks
Ps.: I'll fix the pot blue wire loose end 

[Rob Strand]

If so, the 2 blue wires (one coming from board, another coming from pot) may connect together to 'circuit out' pin, right?
I may find a ground point. Is the black wire on the pot a ground path?
tks
Ps.: I'll fix the pot blue wire loose end 

Yes, it should work.  The blue wires should connect together and go to the wah pot.
Black is ground -  see below.

Here's some more detailed instructions,

https://www.wah-wah.co.uk/tb4.html
https://www.wah-wah.co.uk/effects/tb4a.png

Yours is the "Retaining Input Buffer" case.   Retaining Input Buffer means the buffer is maintained in effects mode.  (It does not mean the pedal keeps the buffer in bypass mode, as would the case for a Buffered bypass.)

I made these additional notes which might help follow what's gone on.

8 pin connector

When looking at the bottom of the unit:
pin 1 is on left and pin 8 is on right

pin   color   sig
1   black       batt-
2   red       batt+
3   black   wah pot (down/ccw)  } connects to circuit ground
4   green   input jack   } permanently joined on PCB   
                   circuit in   }
5   yellow   wah pot (wiper)
6   l.blue   wah pot (up/cw)   } joined by blue wires
                   circuit output   }
7   violet   output jack
8   nc

*** For true-bypass (retaining input buffer)
- The wah pot should remain connected to the circuit out on the PCB
  ie. the light blue wires stay connected.
- The track between the buffer input cap (C9) and the input jack is cut.
   Normally the cap is permanently wired to the input jack.
- The added wire goes the buffer input cap and becomes the new "circuit in" and the
  existing green wire on the connector is the input jack connection.

[Gargaman]

Thank you very much, sir.
All links were valuable.
I tried to aplly the DPDT switching as show on the article, but there was only wet signal. No bypass signal.
I checked all the points.
Since the mod I was talking about was just a presumption (I don't even move the board to see what was going under),
I decided to go back to the initial wiring diagram.
Then it worked. Job is done.
I may try to figure out what was the plan of the initial mod.
Tks again
PS. the bad swittch says 'made in Italy"
the one I placed is made in China.
Is it possible the switch to break if it is wrongly placed under the foot? (too much pressure after clicking)

[Rob Strand]

PS. the bad swittch says 'made in Italy"
the one I placed is made in China.
Is it possible the switch to break if it is wrongly placed under the foot? (too much pressure after clicking)

Good you got it working.   The old switch could have been damaged by overheating when soldering the wires
for the mods.

Some switches might get damaged more than others.  Normally the moveable part of the switch bottoms out on the threaded part and transfers the force to the enclosure.  Safest to adjust the height of the foot switch so the treadle *just*  activates it (but not annoying to use).

[anotherjim]

That "original" DPDT is weird (looks like it could be made as a 4PDT in that long body) and might have been old before used in that wah. Even the old original Bulgin SPDT switches didn't last forever. But, if the rubber treadle buffers are missing or worn or the switch mounted too high, the extra stress can certainly shorten its life.

The DPDT wiring that didn't work should have worked, but its only advantage is with high-gain pedals. By grounding the circuit input in bypass it stops it from amplifying noise that can radiate into the wiring enough to be audible.

This one is very standard and easier to understand.

[Rob Strand]

That "original" DPDT is weird (looks like it could be made as a 4PDT in that long body) and might have been old before used in that wah. Even the old original Bulgin SPDT switches didn't last forever. But, if the rubber treadle buffers are missing or worn or the switch mounted too high, the extra stress can certainly shorten its life.

The DPDT wiring that didn't work should have worked, but its only advantage is with high-gain pedals. By grounding the circuit input in bypass it stops it from amplifying noise that can radiate into the wiring enough to be audible.

This one is very standard and easier to understand.

The reason the switch is done like it is (ie. grounding the input) is to prevent the switch popping.   There's no 1M/2M2 de-pop resistor on the input side of the buffer input cap (some schematics show it but it's not on the PCB).   Using the common switch wiring will let the input cap float and can cause pops.   That was something I noticed when checking the mods.

[Gargaman]

I may have messed something about the orientation trying this input grounding. It should have worked as Jim said. I've learned on other post that with this system you can leave out the input pulldow resistor. Antonis told about a wiring that ground both in and out of the circuit. I may try on future projects.
Another question I have: vintage fuzz don't like wahs before them because the buffered bypass, right? So when you mod to truebypass the impedance that matters for the fuzz after it is from the out wah circuit when its activate. How much is that?

[Rob Strand]

I may have messed something about the orientation trying this input grounding. It should have worked as Jim said. I've learned on other post that with this system you can leave out the input pulldow resistor.

If you follow the wiring diagram in Reply #3 it will work without popping.
There is no detrimental effect using this wiring.

[anotherjim]

On that make of Wah, watch out for axial lead ceramic capacitors (the mustard tube ones). I've had intermittent ones that fail in tandem with the mechanical shock of the footswitch action. You think it's a faulty footswitch, but it's a cap breaking. Best replace them with film type caps.
Also, you should always check the solder side of the board. The pins of the DC jack frequently break the solder.