About stompswitch variability

[Mark Hammer]

Pete or Aron moved the thread over to the Lounge and appear to have locked it.  But I thought it was important enough to post here again, and if they feel that locking is appropriate, so be it.  I'm merely trying to insert a voice of reason and physical plausibility into the mix.

Take a stompswitch apart.  What you have inside are some contacts poking up from the solder lugs, and a couple of little metal pieces that rock back and forth over a pivot point, based on pressing the switch.  Unless the contacts are made from some exotic alloy in one brand/batch and crap metal harvested from old unwashed tin cans from the recycling bin in another, I can't for the life of me see how there could be any audible difference based on the internal contacts themselves.  Does the metal make a difference when running a 20ft cable from a hifi amp to a tweeter?  Quite likely.  Assuming no corrosion whatsoever, would the metal make a difference over a distance of 2mm?  Not bloody likely.  Indeed, the only physical aspect of the switch itself that bears a risk of malfunctioning is the little plastic pivot part that moves the rocker contact back and forth.  These are known to break and some makes may break easier than others.  But this is a matter of "losing the click", not of having the click but losing the contact.

The fact remains, however, that some folks DO experience "bad batches" and inconsistent performance over time.  Some may well even hear legitimate audible differences, not just switching failures.  So what gives?  They can't ALL be crackpots and whiners, right?

Here's what I think happens...

Take a switch apart and look around.  Inside the switch is a little bit of goop to keep the rocker contact from falling out of place.  It's like a thick lubricant .  Sometimes when you open up a switch, you'll find it located only around the pivot point in the middle where the rocker contacts sit.  Other times, though, when you open it up, you'll find a thick coating covering the entire lower surface of the rocker contact (where the actual electronic contacts are made, not where the mechanical force is applied), and you'll wonder how the heck ANY electrical contact is made.  From a number of comments made by others over the last few months, plus my own experience, I believe that the goop applied to the inside of the switches may vary in: a) its quantity, hence risk of redistribution, and b) the extent to which it gets flowed by soldering heat over the surface of the rocker contact to interfere with electrical continuity.

Now, whether the goop gets applied manually by some sweet little Oriental lady with 18 mouths to feed in her extended family, or via machine, it seems like there is some drift and variation in the quantity applied across batches of switches.  Perhaps some makes are more attentive to this than others.  Add to this, the tendency for some builders to apply copious amounts of heat to the solder terminals so that the heat from the rocker contacts causes the goop to turn liquid and flow over the surface of the contacts, and you have a recipe for inconsistent switch performance.

Based on this, I will make some suggestions.

1) To reduce risk of causing "goop flow", make sure the contact you are soldering is not physically coupled to anything else when soldering.  In other words if the connection between the centre/common lug and side lug A is open, then lug A is safe to solder.  You can heat that puppy up, and since it isn't touching the rocker contact inside, no heat is transferred to the rocker contact.  To solder the other set of contacts, press on the switch to lift the other set of contacts, and do them.  That leaves the centre/common lugs.  Get in and out quick.  The tinned wire loop suggested by someone here recently seems very very wise to me.

2) If you already have a problem switch, bends the tabs and take the switch apart.  Bet you 10 bucks you'll see a thick layer of goop covering the entirety of the rocker contact.  It's not supposed to look like that.  Wipe it off and clean the rocker contact well.  Heck, get a Q-tip and clean out all the contacts.  I like to put on some Stabilant contact enhancer on the parts I know will touch.  Now, reassemble the switch, making sure all parts are properly seated internally.  Should work like a charm now.  I've rehabilitated a bunch of switches in this manner recently, and none have given me any more problems.

I'm dead serious about all of this.  There is simply no way ANY manufacturer could turn out a product with that high a risk/frequency of component failure and continue to do business.  It can't be a shitty product, but at the same time our own experience here can't be ignored.  That leaves some sort of "mystery variable" which impacts on switch functionality under the sorts of circumstances WE use them in, and the only thing that fits that bill is clearly the heat-sensitive goop inside that can be made to impede electrical continuity, given the variability of our collective soldering styles.

I gather this goop is something that assists the manufacturer in cranking out switches at a high rate by allowing assemblers to not have to fiddle with picking up rocker contacts that have come unseated or fallen out while being inserted.  It isn't necessary for the switch to function, merely helpful to save 10 seconds of assembly time per switch.  And that 10 seconds of labour per switch is factored into their production cost  As end user you can eliminate the goop and the switch will keep on working just fine.  As manufacturer you may need the goop to produce the product cost effectively.

There.  Does that solve a mystery and a problem at the same time?

[chaddhamilton]

Nice Article, Mark!  I've had a few flukey switches myself and up to this point, I just threw them away.  Won't do that again.

Chadd

[calpolyengineer]

Nice article Mark, I always look forward to your next post.

-Joe

[Connoisseur of Distortion]

Mark, how is it that you take a discussed topic, think on it for a little while, and kick out an answer with a solution in a day or so??

great idea! might have a look inside some switches and see about this mystery goop...