Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old January 15th 16, 08:48 PM posted to sci.electronics.repair
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Default Key contact restoration

On 01/15/2016 11:30 AM, Dave Platt wrote:
In article ,
Gareth Magennis wrote:

Is there a tried and trusted way of adding a conductive contact pad?


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.




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

http://www.mgchemicals.com/products/...pair-kit-8339/

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:

http://www.micromark.com/neolube-2-fl-oz,8383.html

John :-#)#

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Old January 15th 16, 09:19 PM posted to sci.electronics.repair
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Default Key contact restoration

In article ,
John Robertson wrote:

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


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

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

http://www.micromark.com/neolube-2-fl-oz,8383.html


That's where I got mine.

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


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Old January 15th 16, 10:22 PM posted to sci.electronics.repair
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Default Key contact restoration

On Friday, January 15, 2016 at 2:47:08 AM UTC-8, mike wrote:
On 1/15/2016 1:22 AM, Gareth Magennis wrote:


The customer has ripped out all the contact buttons on the right side of
the keyboard, the left side set is still in place and working.


I can't imagine you can manufacture new keys at a repair price the
customer could tolerate.


There's a guy who shows up at local ham radio swapmeets and sells
radio attachment gizmos.
He has a 3D printer and claims to be willing and able to make custom gizmos.


It ain't quick, but you could digitize the shape of an ideal key set, get a 3D print of
its upper and lower surfaces (actually, just the lower surface is critical, the upper
can be done with hand tools), and mold your own key sheet.
If left-side and right-side match, you can (with care) dupe a left-side sheet,
building molds by (if necessary) bronzing the model item.

It'd be easier to get an off-the-shelf product, but most manufacturers (google on
"elastomer kepad" aren't big on stocked items.

http://www.eecoswitch.com/wp-content/uploads/2011/08/ElastomerKeypads.pdf

So, are there any similar keypads on any items that have spare-parts departments?
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Old January 15th 16, 10:39 PM posted to sci.electronics.repair
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Default Key contact restoration



"whit3rd" wrote in message
...

On Friday, January 15, 2016 at 2:47:08 AM UTC-8, mike wrote:
On 1/15/2016 1:22 AM, Gareth Magennis wrote:


The customer has ripped out all the contact buttons on the right side of
the keyboard, the left side set is still in place and working.


I can't imagine you can manufacture new keys at a repair price the
customer could tolerate.


There's a guy who shows up at local ham radio swapmeets and sells
radio attachment gizmos.
He has a 3D printer and claims to be willing and able to make custom
gizmos.


It ain't quick, but you could digitize the shape of an ideal key set, get a
3D print of
its upper and lower surfaces (actually, just the lower surface is critical,
the upper
can be done with hand tools), and mold your own key sheet.
If left-side and right-side match, you can (with care) dupe a left-side
sheet,
building molds by (if necessary) bronzing the model item.

It'd be easier to get an off-the-shelf product, but most manufacturers
(google on
"elastomer kepad" aren't big on stocked items.

http://www.eecoswitch.com/wp-content/uploads/2011/08/ElastomerKeypads.pdf

So, are there any similar keypads on any items that have spare-parts
departments?






Yes, that is exactly the question here.

I need to cannibalise a contemporary keypad assembly that has conductive
pads at least 5mm diameter.

Failing that, I need to make my own rubber knobs, and somehow incorporate
conductive rubber 5mm pads to operate the PCB switch pads.



I don't think this is actually possible in any kind of reasonable
time/effort scale.



Gareth.




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Old January 15th 16, 10:53 PM posted to sci.electronics.repair
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Default Key contact restoration

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 !

Gareth Magennis a écrit :
Hi,

I have a very old synthesiser where the top panel rubber contact
switches no longer work, because the owner has removed the contact strips.

This is the synth:
http://www.vintagesynth.com/sci/stk.php


The contact rubbers are pretty much 10cm x 10cm x 10cm cubes, but they
have a rather large contact footprint.
The corresponding PCB contact gap between the two lands that need to be
bridged is also rather large.
http://tinypic.com/r/14xdmo3/9



So, I am looking into the possibility of replacing the missing buttons
by cannibalising a somewhat more contemporary keypad that has extra
large contacts.

Here's a typical example I found at Farnell. It might be possible to
cut it up and glue it to the keyboard and make things work, if the
contacts are large enough.
http://uk.farnell.com/storm-interfac...rey/dp/9810064




Anyone any such experience here?

I know it's a long shot.



Cheers,


Gareth.






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Old January 16th 16, 06:53 AM posted to sci.electronics.repair
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Default Key contact restoration

On 2016-01-15, Gareth Magennis wrote:
I would direct your juvenile rantings to Microsoft instead.
It is they who have made Live Mail do this, and they won't fix it.


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.
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Old January 16th 16, 10:32 AM posted to sci.electronics.repair
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Default Key contact restoration

On 15/01/2016 08:24, N_Cook wrote:
On 14/01/2016 23:01, Gareth Magennis wrote:
Hi,

I have a very old synthesiser where the top panel rubber contact
switches no longer work, because the owner has removed the contact
strips.

This is the synth:
http://www.vintagesynth.com/sci/stk.php


The contact rubbers are pretty much 10cm x 10cm x 10cm cubes, but they
have a rather large contact footprint.
The corresponding PCB contact gap between the two lands that need to be
bridged is also rather large.
http://tinypic.com/r/14xdmo3/9



So, I am looking into the possibility of replacing the missing buttons
by cannibalising a somewhat more contemporary keypad that has extra
large contacts.

Here's a typical example I found at Farnell. It might be possible to
cut it up and glue it to the keyboard and make things work, if the
contacts are large enough.
http://uk.farnell.com/storm-interfac...rey/dp/9810064





Anyone any such experience here?

I know it's a long shot.



Cheers,


Gareth.




What is the minimum resistance/mm of gap required?


Is it simple on/off contacts or is change of R monitored for key "action"
  #28   Report Post  
Old January 16th 16, 06:31 PM posted to sci.electronics.repair
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Default Key contact restoration

On Fri, 15 Jan 2016 11:15:52 -0800, Jeff Liebermann
wrote:

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:
http://www.siliconeforbuilding.com/pdf/structuralglazing/Data_Sheet_SSG4000_UltraGlaze.pdf
Argh... only 39.


One of my customers, who customizes automobiles, recommended this
stuff:
https://www.freemansupply.com/products/liquid-tooling-materials/mold-making-silicone-rubber/bluestar-addition-cure-silicone-rubber/v-340-mold-making-silicone-rubber-low-viscosity
http://www.miapoxy.com/p-124-bluestar-v-340-silicone-rubber.aspx
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.

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Old January 16th 16, 06:44 PM posted to sci.electronics.repair
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Default Key contact restoration

On Sat, 16 Jan 2016 10:32:36 +0000, N_Cook wrote:

Is it simple on/off contacts or is change of R monitored for key "action"


http://oi65.tinypic.com/14xdmo3.jpg
The piano keys on a synthesizer might require some form of velocity
sensing which most assuredly is NOT resistive. The buttons in the
above photo are for turning things on/off and are therefore simple
on/off connections.
http://www.dummies.com/how-to/content/key-feel-and-response-of-keyboards.html



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Old January 16th 16, 07:40 PM posted to sci.electronics.repair
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Default Key contact restoration

On 16/01/2016 18:44, Jeff Liebermann wrote:
On Sat, 16 Jan 2016 10:32:36 +0000, N_Cook wrote:

Is it simple on/off contacts or is change of R monitored for key "action"


http://oi65.tinypic.com/14xdmo3.jpg
The piano keys on a synthesizer might require some form of velocity
sensing which most assuredly is NOT resistive. The buttons in the
above photo are for turning things on/off and are therefore simple
on/off connections.
http://www.dummies.com/how-to/content/key-feel-and-response-of-keyboards.html




I don't know how many contacts are required.
I just tried taking a standard simple 10x10mm footprint click switch
apart , parts just clipped together. Cutting a disc of thin 1mm
silicone rubber, placing over the dome contact and reassembling , the
click noise and abrupt click action disappears, but still functions.
If they can be soldered to the pcb, ignoring the resistive pads, then
only a matter of fudging the right size and height of top protrusion to
glue over the stem of the switches,if necessary .
Well thats my halfpennyworth


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