Why do footswitches go bad?

[jrc4558]

subj.
Observed deterioration - poor switching between the bypass and effect. When effect engaged, low signal level and lack of treble. An occasional occurence too, sometimes switches good, sometimes - no. The quantity of 'bad' switching attempts increases as the effect remains powered up for more than two hours. I don't understand why. 
Switch in question - Asian copy of the Fulltone 3P2T, the blue one.
Any ideas, gang?
Thanks.

[R.G.]

In a word - they're mechanical.

The bearing surfaces wear. The contact surfaces wear. The springs don't as well anymore. The fit gets worse. The surfaces tarnish and get dirty. The surfaces get roughened up by wear.

In your case specifically, I'd guess it has to do with oxidation on the contact surfaces, or fretting (roughening of contacts in sliding) with wear. But the only way to really tell is to cut it open and look, perhaps with a microscope.

[cd]

9 times out of 10, I'd say bad/poor soldering.

FYI the inside of a typical push on/push off looks like this:

http://www.diystompboxes.com/smfforum/index.php?topic=32254.0

Those two (or three) little "V" shaped teeter-totter things are what make the switch contacts - they have to be lined up perfectly with the solder lugs in order to make the switching work.  Misalign one lug due to too much heat, the switching action is ruined.

[BDuguay]

I've had 2 for sure, and a possible 3rd 'X' style footswitch tank on me. I was able to repair them though. The innards are identical to the ones picture in cd's other post. What failed on mine were those little black pastic pointy bits. They're a spring loaded hollow shaft with a pointed end. Each one operates it's own teeter totter thingy that  connects the middle lugs with either outside lugs. In each case, the pointed end had broken off, likely due to heavy footedness, which in turn caused intermittancy, volume drops, and a host of other unacceptable nonsense. Since everything is enclosed inside the body of the switch, none of the parts were lost and I was able to glue the points back onto their shafts and rebuild the switch. I've had Carling switches apart and they're a similar build only the mechanisms inside are not plastic.
B.

[DDD]

Often reason - overheating during soldering or\and flux contamination on the contacts.

[Paul Perry (Frostwave)]

Often reason - overheating during soldering or\and flux contamination on the contacts.

I think DDD is right on the money here. I've been suprised tht some switches seem to have a fairly low melting point body, so if you are not careful, you can overheat the pins & end up with the switch physically distorting. Plus, I expect that some internal grease around the switch mechanics can melt & get onto the contacts as well. these damned switches (ALL brands) are the bane of our lives.. which is why Boss etc never use them. Want true bypass? use a Boss arrangement driving a miniature signal relay.

[A.S.P.]

then again: audio-crackling footswitches often will be good enough for switching relay-current - and a cheaper 1P1T will do...

[Bernardduur]

I once bought an "expensive" footswitch (I needed one and they had no others) and it died on me after approx. 25 stomps.

Opened it up, reset all and now it still works (after 5 years)....... Sometimes I hate those things.

[Paul Perry (Frostwave)]

One reason we have so much trouble wiht "our" stomp switches, isthat they aren't designed for audio work. They are designed for controlling mains power to motors, and any crap on the contacts simply blasts off. Really.
Whereas, an 'audio' small signal switch has tiny contacts, hopefully plated with some incorruptible hard wearing substance.
So, to be honest, we are attempting the impossible.

[Mark Hammer]

I would also maintain that while these switches are ideally designed/intended for a nice clean on-axis pressing motion (perfectly perpendicular to the housing), they are too often installed in locations and at heights that almost assure they will be stepped on off-axis, causing lateral stress and eventually unpredictable performance.  I have a couple of older Carlings from some ancient pedals I gutted, and quite frankly they are just plain "wiggley".  The amount of lateral play is way in excess of what you find on even the cheapest DPDT switches.  And of course, they are noisy.

Is there a way to avoid that?  I think so.  First off, the plunger should be as close to the surface of the chassis as possible, with only enough collet thread poking up to secure the nut/washer (smaller plungers would be good too, and you often see these on high-end pedals that get switches made for them).  The higher up the  plunger head sits, the greater the lever-like pressure is that one applies by off-axis foot pressing, and the more lateral stress is created over time.  Second, the switch should be located in a spot where, when the way you pivot your foot is taken into account, you are more likely to be pressing the plunger down, and not just mostly down with a bit of sideways thrown in for good measure.

That latter part often requires careful planning of where you put your jacks and battery, and the circuit board too, I suppose.  Of course, it requires some knowledge of how people use their feet too.  Ideally, switches should last longer when mounted on a sloped front chassis, where a user pivoting on the heel of their foot will be able to depress the plunger in a nice clean on-axis motion.  At the same time, sticking a stompswitch in the middle of a chassis where foot pivoting is impossible may *require* the user to hold their foot over the pedal and necessarily press downward, perpendicular to the floor.  It's one of those "ergonomic" things, and you'll have to use your judgment in each instance.

Of course all of this is entirely separate from the sort of chemical/moisture environment your pedals and switches happen to be used in.  I haven't tried it on any of the 3PDT's, but I did pop the cover on a couple of old Carling DPDT's, cleaned up the contacts, applied a bit of Stabilant contact enhancer, and replaced the covers.  Haven't installed them in anything, but testing the contacts with the meter indicated that such interventions did not harm the switch.  Maybe the thing to do for anticipated harsh environments is some sort of chemical contact prophylaxis.