Re: Key contact restoration

Anyone any such experience here?

>I know it's a long shot.

Google for "mold your own rubber parts" or "cast your own rubber parts". Lots of lousy videos on YouTube on how to mold rubber parts. I use Plaster of Paris for the mold, Devcon Flexane 94 Liquid 15250 two part urethane rubber and Vaseline or silicon grease for mold release. Careful when storing the stuff as the stuff in the bottle attacks the bottle and causes it to leak. It cures in 10-15 mins, so be prepared to work fast. Although it's made for making flex molds, it's also the right stuff for making fairly hard rubber buttons, gaskets, shock mounts, seals, etc.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
 Click to see the full signature
Reply to
Jeff Liebermann
Loading thread data ...

Maybe a kit would be better than doing it from scratch: (I haven't tried these).

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
 Click to see the full signature
Reply to
Jeff Liebermann

The resin part of this evidently contains some isocyanate monomers; careful with that! :)

Reply to
Kaz Kylheku

As do most polyurethanes, including PU varnish, where it acts as a moisture-triggered catalyst for polymerisation. I don't think these have much to do with Jeff's cyanide experience; the main worry is allergic sensitization.

Reply to
Clifford Heath

It's a good idea to de-air the mix in a vacuum flash for a while after mixing. It's amazing how much air gets in - until you see the bubbles magically appear as you apply vacuum it's hard to believe.

Reply to
Clifford Heath

Beware the smell of bitter almonds (apologies to Sherlock Holmes): I've smelled them while plating some copper PCB edge connectors with electroless silver, which is basically silver cyanide. When I tasted the rotten almonds, I was already in a stupor and had to be dragged from the building for some fresh air. I've worked with Flexane 94 a few times and survived. Wear gloves and don't inhale the vapors: At 10-20% of solution by weight, it's not going to be very potent.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
 Click to see the full signature
Reply to
Jeff Liebermann

Sounds like you would not want to be under the influence of a "seven percent solution" at the same time!

Mike.

Reply to
MJC

Look, you quoted Jeff without using the correct > characters,

*including his signature*, and put your reply after the signature!

Without the > characters, it looks like your posting is a plagiarism of Jeff.

When I went to reply to you, your entire reply disappeared, because your reply looks like an extension of Jeff's signature, and a proper news client removes everything after the "-- " signature mark when you reply. I had to copy and paste the above from the terminal.

Please use Usenet correctly or FOAD.

Reply to
Kaz Kylheku

Search for a rubber keypad repair kit: There are videos on YouTube on how to apply the stuff. My favorite mistake was to apply too much graphite paint. It's not very flexible and will tend to crumble around the edges. Loose pieces of conductive graphite inside the switch is not a good thing.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
 Click to see the full signature
Reply to
Jeff Liebermann

Oops. The Devcon Flexane 94 is probably too hard and stiff for your rubber button that has to bend and act as a spring: Something more like RTV (silicone rubber) will be more flexible. I have a Shore A Durometer (rubber hardness meter) and can measure a few random rubber buttons and see what's appropriate. Well, the assorted TV remote controls run 53 to 60. Various other rubber buttons vary from 50 to 65. All my music keyboards have hard plastic buttons, so that's not going to work.

I found a part I had made using Flexane 94, which shows 85, so that's much to hard to flex. I don't have something handy that will work, but I'll do some catalog searching this weekend. Offhand, I would suspect that bathroom caulk, rain gutter seal, or other commonly available silicone rubber compound might work but might also be too soft (typically 25 to 30 durometers). Structural silicone might be harder. Digging: Argh... only 39.

These might help: "Using Silicone Caulk as a Mold Material"

Durometer Hardness Scales:

MasterBond Adhesive hardness:

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
 Click to see the full signature
Reply to
Jeff Liebermann

For what it's worth: I've had pretty good luck restoring conductive pads using a product called Neolube #2. It's a water/alcohol suspension of extremely fine graphite, with a small amount of a thermoplastic resin (possibly cellulose acetate?) as a binder. It can be applied with a fine brush or Q-tip.

I recently purchased a bunch of surplus Kenwood UHF mobile radios. About half of them had intermittent or non-working keys on the molded keypads. The pad sheet had originally been made with some sort of sprayed-on or molded-on conductive coating, and I could see where it had been worn off the keys in question (the rubber was shiny and I could actually see the shapes of the corresponding PC-board traces).

Cleaned with alcohol, painted on a couple of thin coats of Neolube, and they work fine.

I can't swear as to how long it will hold, but Neolube seems to have a respectable "grip" on the surfaces I've painted it onto. Its info sheet is interesting... they talk about how its carbon is so pure than neutron activation of contaminants isn't an issue, and so it's rated for use in nuclear reactors.

Reply to
Dave Platt

I can't find a distributor in Canada for Neolube, however MG Chemicals makes a product for renewing rubber contracts:

formatting link

Available in Vancouver from Main Electronics and RP Electronics.

Not cheaper than the US stuff...

In the US you can get it from Micro-Mart:

formatting link

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup) 
John's  Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
 Click to see the full signature
Reply to
John Robertson

The lawyers might have something to say about enforceability in that case :-)

That's where I got mine.

Warning: for a tools junkie, the Micro-Mark catalog is dangerous.

Reply to
Dave Platt

First, clean the PCB with domestic alcool or the good old KF from Siceront KF (Now F2). Second, rip the keys contacts with fine abrasive so it is clean. Third apply some (silver) conductive ink (Microworks for instance).

It's done (let dry 10mn).

I did it for a TV remote control and it works perfectly.

The more simple is often the best !

Contacts are around 0.1 ohm !

Reply to
Look165

Using Live Mail even though it sucks and you know it is *your* choice. Why *should* they fix it when hordes of lemmings will use a free piece of crap as-is? You're the reason they won't fix it.

The responsibility for conforming to Usenet guidelines is yours alone; you can't deliberately use some program you know is broken and blame it on the programmers.

*That* is juvenile; a seven-year-old can easily be found who has a more sophisticated view of the world than this.
Reply to
Kaz Kylheku

One of my customers, who customizes automobiles, recommended this stuff: Note the 400% elongation before tearing. Ideal would be 45 to 50 durometer, so methinks the 45A version might work best. He didn't have a cured sample, so I dumped a blob on a piece of wood. We'll see what it looks like on Tuesday.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
 Click to see the full signature
Reply to
Jeff Liebermann

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.