wah pedal trouble

[Seeksound]

I was replacing the switch in my Crybaby GCB-95 with a 3PDT but couldn't get the wah function to switch over, so I tried the old switch again and it's the same thing. In "off" mode, I've got a clear guitar signal, but in "on" mode, I've got nothing. Does this sound like a tranistor or something similar has blown? I'm stumped. I've got a multimeter but so far have never used one. Any help would be greatly appreciated.

[Mark Hammer]

Unless you used a blowtorch to solder the wire leads, it is unlikely you did any damage to the wah circuit. More likely, you did damage to the switch itself, or else simply wired it up wrong.

Over the last decade I have heard enough whining about "crappy switches" to realize that whomever makes the switches ought to actually be out of business if they actually have that same failure rate with the commercial clients who order these things in the thousands.

One day, I took a stompswitch apart and found the reason why they often fail hobbyists. Inside are either 1, 2, or 3 (depending on whether its a SPDT, DPDT, or 3PDT switch) little brass electronic see-saws. When you hit the switch, one side goes up and the opposite side goes down, making contact. During assembly, the manufacturer applies a little dab of grease to the pivot point. The grease holds the little see-saw in place so that it doesn't fall out, and also damps some of the vibrations that would occur once assembled. It is not electronically essential, but it is helpful.

Trouble is, where manufacturers have ultra-fast soldering techniques, hobbyists and amateur repair folk often do not. The prolonged heat applied to the solder lug can be transferred along the little see-saw contact inside, and if hot enough it melts the dab of grease. The grease then flows along the contact, and acts like an insulator, blocking contact between the little metal piece and the inside part of the solder lug.

If you pry the tabs up...VERY GENTLY...you can take the switch apart, and be able to re-assemble it later. You will probably see the grease coating one or all of those rocker contacts. Clean the grease off well, place the contact back in, and re-assemble the switch, and it should probably work again.

All of that assumes that the issue is the switch and not a miswriring of some kind.

[Seeksound]

Mark, I can't thank you enough man. I wish I had the energy to try that right now but it will have to wait. I appreciate the detailed explanation and it makes perfect sense.

Roger

[Mark Hammer]

My pleasure. Trust me, you are one among many thousands of first-timers who have attempted a "true-bypass upgrade" only to be met with grief.

There are a few things you can do to reduce the likelihood of failure in the future:

1) Make sure all surfaces are shiny and free from tarnish that will slow down soldering. I generally scrape the surface of solder lugs with an X-acto blade first. Sometimes, I even have to scrape the strands of the wire too.

2) Apply a bit of liquid flux to both the lugs and bare wire with a cotton-tipped applicator to enhance solder flow.

3) Tin the lugs and wire first, making sure to leave a bit of time between lugs so that heat does not build up.

4) The heat is conducted to the grease via the rocker contact, and the rocker contact acquires that heat by being in contact with the inside of the solder lug. If you have a meter, or even simple continuity tester, make sure that the outside lug you are soldering is not electronically connected to the common lug in the middle. That way, you'll know the heat is not being transferred directly. The middle lugs are never NOT in contact with the rocker contact on the inside, but at least that's only a couple of risky solder joints to be made.

5) Make sure the tinned wire is stripped back far enough that you can bend it and hook it snugly into the hole on the lug.

6) Solder the whole mess quickly.