ever seen the inside of a 3PDT? (pics)

[choklitlove]

i had a switch that didn't work after use in a few pedals.  i was curious.

here's the initial split:


this part taken out:


that part tilts with each push, and presses on either side of these three plates:


they rock back and forth on the center poles, which are higher than the outer connections, and the plates connect to either of the 2 outer connections of the 3 poles:


here's the push/spring action:


and here's all of the parts:


so now, i see that these could actually be pretty easy to repare.  the main thing i could see causing a switch to fail is the height of the middle poles changing because of heat melting the plastic/rubber holding them. 

i can't remember exactly where this certain switch came from, but maybe smallbear.  i'm not positive, but i bet all are almost exactly like this one.

[JimRayden]

A thing I've been waiting for so long... Thumbs up!

---------
Jimbo

[KerryF]

Nice.  I recently took apart a horribly cheap SPDT switch that I used and for some reason its plastic was melting as I soldered, and it did something to the inside where the toggle wouldnt flick to the other side.

[markm]

Very cool......simple but cool.
I'd like to see this one go into the Wiki 

[darron]

thanks for the scope! good post (:
good point with the excessive heat thing. it's nice to know where they have the potential to be easily damaged. if any pin goes out it could throw out two more.

[Meanderthal]

 Yep, just like a dpdt toggle switch I had to fix once. One of those metal rocker tab things had gotten turned sideways somehow jamming the whole thing up. Easier to fix than I thought.

[birt]

nice pictures. i took a broken one apart too. also an SPDT wich had a plastic pin in the pushbutton instead of the metal one seen here. that broke so the SPDT isn't repearable.

[BDuguay]

The 'X' type DPDT switches are similar in construction. I've had a couple of them fail and was able to repair them. It turns out both had the same problem. The black pointy bits in the second picture were the culprit. The pointed ends had broken off causing all sorts of grief.
I was able to glue them back on and now they work fine.
B.

[petemoore]

 here's tips..
Hot Iron
  Hot Iron preheats pretinned wire just prior to both these hot masses being applied to the switch lug, which had also been tinned, then allowed to cool completely.
  Avoid large globs of solder on the switch lug/wire.
  This should help let the switch be soldered quickly, hopefully the heat doesn't have adequate time to absorb into the internals and cause failure.
  For signal input/outputs, I put the pulldown resistors right on the switch, they form a V Shape [since they both go to ground] and I leave enough resistor lead to do further switch wiring alterations on the thin leads...this leaves the thermal mass of the lug joint to 'buffer' heating between the hot lead and the switch internals.

[Mark Hammer]

I've posted this before but since you have the pix here, it bears repeating since it might make more sense here. 

Those rocker contacts are often initially held in place on the middle of the three contacts with a small dab of grease.  Indeed, you can see some residue of it here: http://i49.photobucket.com/albums/f295/choklitlove/3pdtinsideplatesremoved.jpg

I have no idea how the grease is applied, but it is sufficient to make the rocker contact stick to the middle "saddle" type contact during assembly, so that they stay seated properly despite jiggling around when the tabs of cover (http://i49.photobucket.com/albums/f295/choklitlove/3pdtspring.jpg) are pinched shut.  Presumably, there will be some variation in amount applied.

SOMETIMES it can happen that spending too much time flowing a solder joint results in the heat building up, and the grease being melted and flowing along the rocker contact.  If there isn't too much grease the switch continues to function, but if there is a bit too much grease and too much heat, the contact becomes essentially coated with this nonconductive substance and fails.  There ARE other reasons for switches failing but the rate of failure often reported seems so excessively high, that it seemed to me that user error must play some role.  And this would seem to be the way (or at least a common one) in which user error produces failure in an otherwise decent switch that worked when it left the factory, as well as when it left Steve's or Aron's hands.

The good news is that you can see the construction here, and can easily see that these rocker contacts CAN be safely removed, cleaned up of any grease, and successfully reseated to restore switch functioning.  I've "rehabilitated" a number of switches this way myself, and as long as you take care to save all the parts during disassembly, and not overstress the tabs on the cover, you should be able to repair your own switches as I did.

[Pushtone]

Since these type of switches where originally intended for
switching 120 volts would there be any advantage to building a "burn in" rig?

The original use was vacuum cleaners. Vacuums draw an amp or two so how about
burning in the footswitch at 120v with a 3 amp load for 30 minutes?

That should warm it up.

[Paul Perry (Frostwave)]

It's not really a matter of "burning it in" as "flashing it in", these switches are assumed to be switching AC & self-clean as any crud on the contacts is vaporised durig switching. Any switches designed for low-level audio switching, have totally different contact materials and design - but we have to take what we can get.

Since it's a curent thing, you caould make a flashing rig from a low voltage transformer driving a suitable load, if you want to avoid the mains (for safety reasons). I wouldn't use a DC source (like a car battery) because, with DC, you get a much bigger arc (AC arcs self-quench on the cycles) and might actually damage the contacts.

[Processaurus]

Since these type of switches where originally intended for
switching 120 volts would there be any advantage to building a "burn in" rig?

The original use was vacuum cleaners. Vacuums draw an amp or two so how about
burning in the footswitch at 120v with a 3 amp load for 30 minutes?

That should warm it up.

Weren't these taiwanese 3pdt switches designed specifically for stompboxes a couple years ago?  For EH?  Wonder if they're even rated up to 120?

[choklitlove]

this was posted in the picture thread:

The only thing I like better than the blue 3PDT is that it´s acoustically quieter, Those blue ones are quite noisy. CLICK!!! CLICK!!! when you step on them!!! Not a problem if you play loud, but if you don´t...
Morocotopo

it just reminded me how i have this problem.  the 3pdt's are too loud for me when pushed.  does anyone have an idea of maybe a way to remedy that from the inside of the switch?  there's gotta be a way.

[zachary vex]

presumably a weaker spring would reduce the "click" level, but i think it would also decrease reliability.  the hard "click" ensures that the metal teeter-totters make solid contact, biting through any impurities/oxidation on the surface of the metal.

[Mark Hammer]

this was posted in the picture thread:

The only thing I like better than the blue 3PDT is that it´s acoustically quieter, Those blue ones are quite noisy. CLICK!!! CLICK!!! when you step on them!!! Not a problem if you play loud, but if you don´t...
Morocotopo

it just reminded me how i have this problem.  the 3pdt's are too loud for me when pushed.  does anyone have an idea of maybe a way to remedy that from the inside of the switch?  there's gotta be a way.

One possibility to consider is to use some of that rubbery conformal coating and put just a light coating on the end of that plunger thing you see here: http://i49.photobucket.com/albums/f295/choklitlove/3pdtspring.jpg  You can't/shouldn't put TOO much on because that will compromise the critical spacing.  However, part of the audible click, I think, comes from the shock when that part suddenly flips the plastic rocker panel and comes to a sudden halt.  If a wee bit of rubber softened that blow you should hear less of it...in principle.  Of course, that assumes that whatever one dipped the plunger tip into was softer than the metal shaft but just as slippery.  I suppose it's nothing a bit of 3-in-1 or WD40 couldn't fix.

All in all, though, starts to present a strong case for the many advantages of electronic switches, don't it?

[The Tone God]

All in all, though, starts to present a strong case for the many advantages of electronic switches, don't it?

Ya think ?

Andrew

[Mark Hammer]

I sho' nuff do!

Of course, coming at it from the other angle, there are a lot of folks who rely on the tactile feedback more than the visual.  For a number of situationally appropriate reasons, they need to feel a good stiff "CLICK" when they step, and the stiffer it is, the more reassuring it is.

But there is "click" and then there is "CLICK".  As much as I love the Tone Core pedals, many of them use the single treadle to perform two functions, one of which is often tap tempo.  In order to differentiate the two functions, the bypass requires a much stronger push and a resulting click more powerful than what stompswitchers are accustomed to.  I understand the need for easy discriminability, but I still find it unnerving.

The long and the short of it is that you need to make your switching choices based on multiple considerations:

• easy of installation
• feasibility of remote switching
• feasibility of BOTH latched and unlatched switching
• ease of implementing status indication
• space
• preferred form of user feedback (tactile, audible, visual, etc.)
• spacing/location
• current consumption
• need for complex vs simple switching
• the role of on-board buffering
• cumulative noise over the signal path
• location in signal path

And a host of other things.  It's not always as simple as mechanical=good/bad and solid-state = the opposite.

[The Tone God]

Agreed. They are different tools for different jobs.

On the topic of "clicking" it is intersting that some pedal manufactures that use electronic switching systems which do not have a clicking mechanism (i.e. Boss, DOD, Ibanez/Maxxon, etc.) do not seem have this point brought up or feel the need to try to simulate the "click". I have never heard someone say "I love the sound of that pedal but I won't buy it because the footswitch doesn't click."

I have been a fan of the old foot switches for a long time and will admit to a certain level of almost primal satisfaction of stomping away and feeling that click through my boot but I have been playing with alternate switching mechanisms for years and for now I have settled on a system that has no mechanical feedback and I quite frankly I don't really miss it as much as I thought I would. Maybe the big old pedal producers have already told us how much stompers really like their "click" by the reflection of the designs not having a "click".

Andrew

[darron]

this was posted in the picture thread:

The only thing I like better than the blue 3PDT is that it´s acoustically quieter, Those blue ones are quite noisy. CLICK!!! CLICK!!! when you step on them!!! Not a problem if you play loud, but if you don´t...
Morocotopo

it just reminded me how i have this problem.  the 3pdt's are too loud for me when pushed.  does anyone have an idea of maybe a way to remedy that from the inside of the switch?  there's gotta be a way.

i agree. they are very loud! but, i like that because it makes me think that they must have a much faster action. faster action will mean less time where the signal is cut. i think these switches seem almost seamless, and maybe it's my imaginaiton ,but they seem faster than the x shape dpdt.

also, the noise is not a problem unless you are using it for bedroom use! any reasonable volume, about half of stage volume covers up the click. also, i've never heard it mic'd through the PA before.