The red insulation on 3PDT's...

[jkokura]

How neccessary is it?

I've got a switch that's been soldered and unsoldered a few times now. I'm trying to figure out what's wrong with this pedal I'm working on. Some of the red insulation has cracked and fallen off the poles. Some are still there. How much abuse can these things take before it could be that the switch itself is the problem?

Jacob

[mth5044]

Overheating the switch can cause problems. I'm not sure, but the red stuff may even help keep the lugs in place/connect to the throws. I'm not totally sure on that last part, but I've had a switch that worked, but then crapped out after I re-soldered it.

[John Lyons]

The red stuff is epoxy. It holds the lugs in place as well
as sealing the lugs from contaminants and soldering
flux etc. Epoxy is weakened with heat...

[jkokura]

So is my switch pooched?

Jacob

[puretube]

IMHO: yes.


[edit]: Mark Hammer may be able to help you repairing it... 

[jkokura]

Just before I gave up on it, I wired it up, put it back in the box, and now it's working.

I guess my question isn't whether it will work or not - as it's currently working - but more whether it's ok to leave it in a working pedal? I imagine it won't see much physical wear and tear on that end, but mostly just me stepping on and off the pedal.

What will Mark do to it? Is it worth sending it to him considering the shipping will cost more than getting a new one for $4 from PPP?

Jacob

[puretube]

He will explain, soon  (hopefully)

[Paul Marossy]

If the terminals on the bottom of the switch aren't loose and haven't been overheated to the point where the plastic has melted and the terminals have actually moved out of their place, then the switch is probably fine for a long time to come. That has been my experience anyway.

[Mark Hammer]

"Soon" has arrived. 

Certainly once enough of the red epoxy has broken off to make the lugs wobbly, I would personally declare the switch beyond reasonable repair (though perhaps within "heroic" repair).  Given how much they cost, and how much time you would have to invest to repair it, it certainly would not be worth it to engage in "heroic" measures.

On the non-heroic front, one of the things that happens to stompswitches when too much heat has been applied to the solder lugs is that the grease which physically stabilizes the rocker contacts inside the switch will start to liquify (while warmed up) and flow along the contacts.  Once it does that, it can produce a coating on the rocker contact that will insulate the contact so that it does not make contact.  Here.....finally....is a diagram.

On the bottom, you can see three pins/lugs.  Those solder lugs go through the epoxy to the inside, where they become pivot points and contacts.  The rocker contact is a slightly curved piece of metal (composition unknown at the moment, but I imagine the manufacturer's datasheet says somewhere).  It rests on the middle contact like a see-saw.  When you push the switch down, a plunger slips to one side and pushes it down, resulting in the other side lifting up.  Push again, and the plunge slips over to the other side, causing the reciprocal action.  There is some grease applied to the pivot point in the middle; partly to hold the pieces together during assembly, and partly to physically damp unintentional vibration and "chatter" in the switch.

One side of the rocker contact is always making physical contact with the inside of the solder lug.  When you apply too much heat, that heat is conducted from the outside of the solder lug, through the inner part of it, to the rocker contact, and along the rocker contact, where it melts the grease.

If you gently pry up the tabs on one side of the top half of the switch, you can lift the upper half off and get at the rocker contacts.  Take them out, and clean off the grease with a tissue, or cotton tipped applicator.  You might want to clean off the tops of the inside contacts as well.  Place the rocker contacts back in, making sure to seat them properly on the pivot point.  Then place the top half - with all the parts - back on and press the tabs back into place.  Assuming the components are properly aligned, the switch should function properly again.

[Paul Marossy]

I tried to repair a 3PDT switch once. It was a real pain, wasted a lot of time and ended in failure - I should have just bought a new one. That's what I would do if I ever mess up one again. I've soldered up literally hundreds of them now, and have only ever messed up one. That was the one that I tried to fix! 

[Processaurus]

"Heroic repair"!   What a great term.

[jkokura]

So as soon as this pedal starts acting up I'll replace the switch. Right now, I've finally got this thing working, and I don't want to mess with that by putting another switch in there - cause it's working, and I've been pulling my hair out just to get this working and it finally is.

However, I'll pay attention to how it is working in the future.

I just had one lug lose it's red epoxy. I'll be careful with future soldering.

Also, the theory from Mark is awesome knowledge - I appreciate that very much.

Jacob

[KazooMan]

The "Heroic Repair" may be a Pyrrhic Victory" when you realize you wasted hours of time on a ten dollar switch.

I have had some of the red epoxy give up the ghost also.  I just used a toothpick to work a bit of new epoxy around the lug and it is as good as new.  I was concerned that without stabilization the connections inside the switch might be getting torqued around and would eventually fail.

I have gotten so used to using epoxy to make so many things right that I gave up on the little 10 ml  "syringe" packages and started buying the stuff in the larger bottles.

[Mark Hammer]

Yup.  If it's going to take 30 minutes of your time to take it apart, reassemble, and resolder, then it's worth it.  If it's going to take you an hour or more, yur time is worth more than that; get a new switch.

[Paul Marossy]

I just had one lug lose it's red epoxy. I'll be careful with future soldering.

If it lost all of its epoxy, then the lug would be wiggling around and it wouldn't make a reliable connection. It just lost the part that you see on the outside of the switch. 

[frank_p]

Epoxy is not a very good glue for soldering lugs.  You can de-epoxy any glue joint with heat.  Very sensitive to heating.