EEVblog #1361 - Dodgy Tactile Switch TEARDOWN

By popular demand, Dave tears down the dodgy tactile switch from his aircon, and compared with a couple of others.

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#Teardown #Microscope #Switch

[ncot_tech]

Haha this is epic level trolling.

"Mutter mutter 15 minutes fixing a dodgy switch mutter mutter"
"Really, here's 15 more minutes of me taking that switch apart... enjoy!"

[SwitchAndLever]

Any of you switch afficionados out there? don't mind if I do! 😉

When it comes to these tactile microswitches the difference between the cheapest of the cheap and the good quality "expensive" brands like ALPS is actually surprisingly low. Yes, they look a bit rougher around the edges, but if things like bouncing isn't a big issue for you they will perform just about the same. Even the cheapies last for a ridiculously long time, as you know from your look at snap domes in the past. I definitely think the failure of your switch was due to mechanical wear on the plating, which when worn through opened up for tarnishing with a less conductive oxide.

I would contact an ALPS rep in Australia. They love sending out sample packs. They have these beautiful "catalog" boxes which open up with a beautiful display of many of their switches which you easily could just spend an entire wonderful afternoon flicking and clicking. They have a broad selection of snappy ones like these all the way to really nice soft touch long travel ones too. Truly a sight to behold!

This was way more interesting than I may have thought. Thanks

[almostanengineer]

Now this is the random EEVBlog stuff I subscribed for 😅

[redpheonix]

1:15 - 1:33 Oh, really? So THAT'S why some of my older equipment thinks i'm pressing buttons other than the one I'm actually pressing! I've wondered this for years, and never really figured out what could possibly be wrong!

Huh...!

[OneBiOzZ]

i took apart one of these switches once when it failed on an old scooter charger
the dome was totally etched through, the switch put 5v across a pulldown in to a 2.2u cap ... the pulldown was 4.7 ohms and passed an amp
i assume someone at some point forgot to put in a 'k' in the schematic and it simply worked and no one caught it, but that poor 1/4w resistor and 7805 survived

but for this i assume repeated pressing etched away a criminally thin plating of silver and let it oxidize

[SeanBZA]

Silver oxide is reasonably conductive, the black is silver sulphide, which is an insulator, or at least a poor resistor with 5V applied. Silver plated with a thin coat on the one side of brass sheet before being punched out and into the die to shape it. The more expensive uses stiffer and harder nickel, which is more resistant to corroding, and can get by in regular atmosphere with no coating on it, but yes for the best you want heavy gold plating on the disk and the body contacts. A flash coat will work for a while, but will wear away, making the contact problem worse.

Body on the cheaper ones is only going to be tin plated, because silver is expensive, and tin plate is good enough to pass initial testing. Likely stamped out of a long roll of tin plated steel, and then used in a long strip to injection mould a load of switch bodies, then punched out and formed after assembly.

[scowell]

Thanks for the dive... I was going to suggest that you take the actuator from the bad switch and move it to a new one... melting the top down should be not too hard. Now I want to see the original switch fully repaired! Get some silver polish and a Q-tip and then treat it with Caig Labs magic liquid! Rotate the dome 90deg. I've done switch repair with vintage musical equipment, you can drill out rivets and use 2-56 hardware to bolt them back together.

[hoffmannolsen]

Ah, that is why my old Denon DVD player believes I'm pushing the hdmi type button when I'm actually pushing the eject button. I always thought that it had to do with a bad seated flex cable or even a broken flex cable. Thanks for this video!

[MrJohnBos]

This video was definitely very interesting. Who knew what was inside. As always, thanks for your fantastic and informative videos. I've watched so many I'm developing an Aussie accent.

[anarchist]

It's a plastic dust compacted and stuck to the bottom of the dome. Heat it up - it should show itself right away.

[JonathonPawelko]

I have repaired and replaced various micro switches with and without micro controllers, unfortunately as a rule they are not made to be replaced. Good to see the effort though. Cheers from Canada.

[PrinceWesterburg]

Silver does oxcidise but silver oxcide is still very conductive.
Great video - I must get around to fixing a mate's synth with dead keys!

[bcs]

I just finish fixing one 2 days ago and now this video pops up!
Mine failed in the exact same way.
As a temp fix while waiting for a replacement, I scratched off the oxide layer and the switch is working again (for now)

[jasonshackleford]

Is it just me or does the package for the "CNK" say "CKN"

[thenoisyelectron]

That camera is absolutely fantastic holy shit.

[JKtheSlacker]

"It's probably easier just to go down the shaft really and then squirt the whole thing" - Dave Jones, 2020

[djwilliams]

that era of tact switches were very prone to failure. Contact cleaner would never really help; replacing the switch always did. Glad to finally see the failure inside. One would assume an issue with the material used for plating?

[pekkagronfors]

My Roland D-50 needs several of those small suckers exchanged.

[philipp]

So the common failure mode is galvanic corrosion on the tactile dome, because the silver plating is soft and thin wore through?