[CW] Clean Contacts

Fri Aug 12 14:28:39 EDT 2016

New to CW as a no-code Extra here, but I've got about 20yrs experience in connector and contact design. 

Nature abhors a vacuum, but only a little less than that, she hates clean, pure, shiny metal surfaces. 
So you get atmospheric oxides that love to glom onto those surfaces. 

The key to a good contact is normal force. That's the force perpendicular to the contact interface, which may not necessarily be in the same direction as downward force on a key. 
Net to that is lateral wipe at the contact interfaces - even a little. The lateral motion breaks up the surface scum (on both pieces) and exposes fresh metal on a molecular level. 
(So there's plenty of wear life in a keying mechanism.) But, d epending on what kind of cruft is accumulating on the contact surface and the geometry of how the two conductors come together, a knife edge on a pad, or a point to pad contact may not displace the oxide film. In a good contact interface, the moving member acts like a teeny snowplow so under a microscope you see 'snowbanks' of less-conductive gunk building up past the end of the wipe path, and if they are left to grow too high, a contact beam can slide past the previously wiped 'good' landing area, and crawl partway up the less-conductive ridge of gunk instead of plowing it further along the wipe path. Mechanically cleaning the contacts takes the peaks off these ridges,, and some cleaning products attack these compounds without corroding the base metals. 

My fav over the years was 'Relay-Kleen' which I think Amphenol used to sell. Then it went off-patent and it's gone, and now replaced by a couple dozen no-name knock-off products. 

If your contacts are plated, two more ugly problems can happen next: The obvious one is plating wear-through, which will cause noisy, variable resistance as the contacts close. 
The other thing that's a lot harder to deal with is substitution on a metal lattice level. You see this in gold-plate over nickel-plate systems; the base metal (brass or bronze) copper switches off with the nickel over time, and some of them end up making it into the gold. These intermetallic compounds are a LOT less conductive than the pure metals, they are glassy and often quite hard, like agate. 
Contact wiping motion will burnish or polish these impurities and extra-harden them. Contact cleaner solvents won't attack them much, and you're pretty much stuck with mechanically removing this stuff and re-plating, or living with base-metal to base-metal contacting, which is a poor second choice, but may work for short-term, emergency operations. 
Keep the current low, so you don't get micro-level spot welding and fretting off of the materials. 

- GLL 

----- Original Message -----

From: "D.J.J. Ring, Jr." <n1ea at arrl.net> 
To: "CW Reflector" <cw at mailman.qth.net> 
Sent: Thursday, August 11, 2016 8:04:22 PM 
Subject: Re: [CW] A keyer ruined my wrist... 

I agree with what's been said, but I'll add that an old timer told me that if the two sides of a contact meet ever so slightly NOT flat to flat, the contacts will automatically clean them selves by sliding. 
Also if you have domed contacts, do NOT file them into a flat because domed contacts are better. N2DAN used domed contacts on his paddle for example. 
73 
DR 

On Aug 11, 2016 10:01 PM, "Benny Owens" < k5kvm5 at gmail.com > wrote: 

RON 

YOU HAVE GOTTEN SOME GOOD ADVICE. I TOO USE THE W0EB DOT STABILIZER 
ON ALL THE BUGS I USE. 

CLEAN AND POLISH THE CONTACTS. CLEAN AND CHECK THE PIVOTS FOR GOOD 
GROUND. YOU CAN DO THIS WITH A GROUND JUMPER AROUND THE PIVOTS. 
CHECK YOUR CONTACT ALIGNMENT. THE CONTACT FACES SHOULD BE PARALLEL AS 
THEY TOUCH. ALIGN ON ALL THREE AXIS. THERE ARE SEVERAL YOUTUBE 
VIDEOS THAT SHOW HOW TO ADJUST A BUG. THEN THE DOT STABILIZER CAN DO 
ITS JOB IF NEEDED. I LIKE THE WAY IT STOPS THE TRAVEL OF THE DOT 
CONTACT ON SEPARATION. 

I FOUND MY BUG FIST IMPROVED WHEN I RETIRED MY PADDLE A COUPLE OF 
YEARS AGO. I HAD BEEN USING BOTH SINCE 76. 

73 
BENNY K5KV 

On Thu, Aug 11, 2016 at 8:01 PM, K3PID < Ron.K3PID at sbcglobal.net > wrote: 
> Boy who knew that a few years of using a paddle and a keyer would ruin a 
> guys wrist? My hand just doesn’t want to make multiple DAHs ( cause the 
> stupid keyer does it all by itself...) I’ve been practicing off-air and it’s 
> coming back but what a struggle! 
> 
> ALSO!! Why are the DITs from my new bug scratchy? Right count, right 
> length, just not clean! Is this a possible spring tension thing? or am I 
> just having to relearn it all? Is there a contact wetting required? I don’t 
> recall having the issue in the past... 
> 
> 73 ES AS while I work it out... 
> 
> Ron K3PID 
> 
> 
> 
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