Adventures in switch-cleaning

[Mark Hammer]

A couple of guys came over on the weekend and we had a small pedalfest.  One of them had a Klon clone on his pedalboard that was built for him by his electrician brother-in-law and sounded as good as you might expect...when it was able to switch on.  The switching was intermittent.

I popped the back off.  Happily, there was enough slack in the connecting wires that I could pry the tabs off the blue 3PDT, disassemble it and peer inside, without having to unsolder anything.  Sure enough, there was grease all over the rocker contacts.  Took the contacts out, cleaned them off with a paper towel, applied a dab of Stabilant to each end of the 3 contacts, and reseated them using tweezers.  Put the two halves of the switch together, squeezed the tabs shut and screwed it back into place.  Not ten minutes from start to finish, he had a properly-functioning pedal that switched reliably.

I don't know what makes it that way, but switches often come with obstacles to rapid soldering.  I think people need to take steps to assure as rapid and non-heat-accumulating an approach to soldering switches as they can.  The fellow who built the pedal had done, in my view, a very respectable soldering and wiring job all round.  But, for whatever reasons, too much heat had found its way into the innards of the switch and caused the grease to flow.  The grease is supposed to be in there, and does serve a useful (though not absolutely necessary) function.  However, when it has been encouraged to misbehave by heat build-up, the only practical course of action is to remove it.

So, once again (with feeling), some guidelines for having your stompswitches not disappoint you:

1) Make sure the solder lugs on your stompswitch are clean and shiny.  Scrape any tarnish off with a utility knife or whatever works for you.  Oxidation will impede solder adhesion/flow and require application of heat for a longer period to achieve solder flow.
2) Apply some liquid flux to the solder lugs.
3) When you solder the outside lugs, do a continuity test first, and make sure the rocker contact is not touching the middle and outside lugs at the same time (i.e., they read open circuit).  This will assure that heat is not directly transferred from the lug you are soldering to the rocker contact...where the grease is.
4) Leave a bit of time for things to cool down, between soldering any two lugs.  If you have something to use as a heat sink, so much the better.  A wadded-up pad of paper towelling with cold water in it will work nicely.

[R.G.]

It may be even simpler. Mark, where is the grease inside the switch? Can the switch be oriented for soldering so that when it softens under heat, the grease runs away from the contacts?

[Mark Hammer]

I think the challenge is that the grease is not necessarily applied, or residing, in a manner that is predictable.  That is, in fact why such switches very often become intermittent, rather than simply failed.  So many of us experience switches that work eventually (i.e., you need to switch back and forth a few times to assure the effect is on).  I figure it is because the grease, in its natural room-temperature state, keeps changing shape.  Think of it like a glop of shaving cream in the palm of your hand.  Poke three fingers of your other hand into the shaving cream, then take them away, then poke your palm again.  The shaving cream will have changed its shape with each action.  The grease acts the same way, such that sometimes it impedes electrical contact, and sometimes it moves out of the way, eventually moving back IN the way.

From looking at the disassembled switch the other day, it would seem that another part of the grease's function is to lubricate the path of the little part that slides back and forth over the top of the rocker contacts, to push them this way and that.  So, the grease starts out on the top of the contacts, and too much heat can cause it to flow to the underside, where the rocker contacts make physical contacts with the inner part of the solder lugs.  I don't think it is a particularly predictable outcome, with respect to directionality, since you have no idea how much the switch may have been depressed prior to soldering and just where that initial sploosh of grease has been pushed to.  The "solution" might be to use rocker contacts that are teflon coated or otherwise plasticized on one side so that there is nothing to liquify.  Or perhaps simply opt for a slightly more costly form of grease that can withstand higher heat before liquifying.  For now, good soldering practice seems to be the best strategy, IMHO.

[Mark Hammer]

Just a quick addendum.

The other fellow who came over brought, among other things, an original Colorsound Overdrive and an Ibanez AFL Auto-Filter.  The Overdrive had erratic behaviour from the Gain pot, going from negligible gain to full-out within a few degrees of rotation, and the AFL oscillated like crazy.

In both instances, the cure involved disassembly of the relevant pots, and a complete cleaning, and application of a bit of Stabilant.  Both pots were a little grimy inside.  The Overdrive simply because of age, and the AFL because it is a slider with too much of an opening for stuff to get in.  Once I was able to restore the proper contact of the wiper to the resistive strip, the Overdrive gain changed more gradually, and the AFL stopped howling and behaved itself.

Remarkable how much misbehaviour of pedals stems from crap getting inside components with moving parts (switches and pots).

[GGBB]

Thanks Mark - great tips.  I never even knew that there was grease inside those switches - I assumed teflon.

[wavley]

I heart stabilant!

[petemoore]

  after baking switch lugs with:
  leads that are so fat they take time to heat up, are difficult to manipulate into position etc.
  Leads that haven't been pretinned...etc.
   These days I use small resistor lead [or similar], pre-tin And Preheat...so the iron, the wire and the solder are already 'just fluid', tucking a thin solder core through the lug eyelet or pretinning quickly the switchlug...makes the solder melting process on the switch lug a quicker, sure-fire deal.
  Solder seems to 'flow best when it's 'fresh'...lengthy heating or high heating 'dries' it, a fresh little dab [teeny dab] added to 'dried/baked' adds fluidity to the 'blob'.
   I didn't want to say solder 'blob' because the smallest amount needed to provide structural rigidity is the right amount, a blob is what a beginner needs to avoid, and what an experienced solderer would quick-heat and remove.

[R.G.]

I think the challenge is that the grease is not necessarily applied, or residing, in a manner that is predictable... sometimes it impedes electrical contact, and sometimes it moves out of the way, eventually moving back IN the way.

Of course, it would be that way.

Yep, good -and quick!- soldering is probably better.

  Solder seems to 'flow best when it's 'fresh'...lengthy heating or high heating 'dries' it, a fresh little dab [teeny dab] added to 'dried/baked' adds fluidity to the 'blob'.

Yep. I believe this is from the build up of oxides on the solder joint. I use a touch of liquid flux from a Q-tip or toothpick for much the same thing. It works in most cases.