I picked up an old Electro Harmonix Muff Fuzz guitar effect box. Not to be
confused with "Big Muff" or "Double Muff" units. Seems pretty simple but it
is "big" to me in regards to figuring out how to fix it.

Here is what it is doing; Guitar signal passes through until I flip the
switch ON, then there is no sound.

Here are pictures of my unit...
http://misterc57.home.comcast.net/toys/muff.htm

I can use a VM and can solder repairs. The pot and the switch seem to be
working. Can anyone suggest what I should check next in trying to fix this?

Much Thanks, Mark