Key contact restoration

[Gareth Magennis]

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-interface/70160101/keypad-storm-700-16way-grey/dp/9810064



Anyone any such experience here?

I know it's a long shot.



Cheers,


Gareth.

 

[Kaz Kylheku]

On 2016-01-15, Jeff Liebermann <jeffl@cruzio.com> wrote:

On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
sound.service@btconnect.com> wrote:

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

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

 

[Jeff Liebermann]

On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
<sound.service@btconnect.com> wrote:

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
<http://www.devcon.com/products/products.cfm?family=Flexane%C2%AE%2094%20Liquid>
<http://www.amazon.com/Devcon-15250-Black-Flexane-Liquid/dp/B00065TLJK>
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
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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[Jeff Liebermann]

On Thu, 14 Jan 2016 17:11:25 -0800, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
sound.service@btconnect.com> wrote:

Anyone any such experience here?
I know it's a long shot.

Maybe a kit would be better than doing it from scratch:
<http://www.alumilite.com>
(I haven't tried these).
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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[Jeff Liebermann]

On Fri, 15 Jan 2016 02:56:51 +0000 (UTC), Kaz Kylheku
<kaz@kylheku.com> wrote:

On 2016-01-15, Jeff Liebermann <jeffl@cruzio.com> wrote:
On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
sound.service@btconnect.com> wrote:

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

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

Beware the smell of bitter almonds (apologies to Sherlock Holmes):
<http://news.wustl.edu/news/Pages/20916.aspx>
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:
<http://www.actiocms.com/VIEW_MSDS/view_language_kits2.cfm?edit_msds_id=4328&dbname=production&language=1&format=16&CFID=11369918&CFTOKEN=1c713f7731a98b98-A229D917-9DA3-18D9-6BC94692623356A2>
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
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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[Clifford Heath]

On 15/01/16 12:11, Jeff Liebermann wrote:

On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
sound.service@btconnect.com> wrote:

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
http://www.devcon.com/products/products.cfm?family=Flexane%C2%AE%2094%20Liquid
http://www.amazon.com/Devcon-15250-Black-Flexane-Liquid/dp/B00065TLJK
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.

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.

 

[N_Cook]

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-interface/70160101/keypad-storm-700-16way-grey/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?

 

[MJC]

In article <5cqg9bh5gv5vnfdgt8dq7gn1clv2sfetm9@4ax.com>,
jeffl@cruzio.com says...

Beware the smell of bitter almonds (apologies to Sherlock Holmes):

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

Mike.

 

I have a stupid question.....are keyboards connected to a connector ? is there an assembly area into the registering circuit ?

 

[mike]

On 1/14/2016 3:01 PM, 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-interface/70160101/keypad-storm-700-16way-grey/dp/9810064




Anyone any such experience here?

I know it's a long shot.



Cheers,


Gareth.

I'm having a hard time reconciling your text with your picture.
Looks more like 1cm cubes?
And the contact is the circular spot on the bottom of the key?
Rather large???
What part got removed by the customer?

I've had some success with very thin tinfoil glued to the bottom
of the conductive pad on the key.
But, I've not worried about longevity of the fix.
Not sure that would be a good thing for a paid repair for a customer.

I did try conductive silver paint, but that flaked off rather quickly.

Also need to clean the pads on the board well, without scraping off
the black conductor.

Another thing I thought about trying was a piece of "zebra strip"
used to connect calculator boards to their display.
Lay it sideways and properly oriented, because you need a long
conductive path to connect the pads
on the board.

 

[Gareth Magennis]

"Jeff Liebermann" wrote in message
news:gvgg9bdishpmu7lsmjm7kenvjqkhh73sr9@4ax.com...

On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
<sound.service@btconnect.com> wrote:

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
<http://www.devcon.com/products/products.cfm?family=Flexane%C2%AE%2094%20Liquid>
<http://www.amazon.com/Devcon-15250-Black-Flexane-Liquid/dp/B00065TLJK>
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
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

---


Thanks, might give that a go.

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


Cheers,


Gareth.

 

[Gareth Magennis]

>
I'm having a hard time reconciling your text with your picture.
Looks more like 1cm cubes?
And the contact is the circular spot on the bottom of the key?
Rather large???
What part got removed by the customer?






Sorry, that's a typo, that should be 10mm x 10mm x 10mm cubes, as the ruler
in the photo shows.
That same photo with the ruler shows the round pad to be about 5mm diameter,
much larger than the key contact strips and button pads I find on
contemporary equipment.
This is old school manufacturing.




Gareth.

 

[Gareth Magennis]

I'm having a hard time reconciling your text with your picture.
Looks more like 1cm cubes?
And the contact is the circular spot on the bottom of the key?
Rather large???
What part got removed by the customer?







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.
The photo shows the right hand side of the PCB with 2 buttons from the left
side put in the photo to show the size of things.



Gareth.

 

[mike]

On 1/15/2016 1:22 AM, Gareth Magennis wrote:

I'm having a hard time reconciling your text with your picture.
Looks more like 1cm cubes?
And the contact is the circular spot on the bottom of the key?
Rather large???
What part got removed by the customer?







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.
The photo shows the right hand side of the PCB with 2 buttons from the
left side put in the photo to show the size of things.



Gareth.

OK,
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.
I never asked the price.
All his samples were rigid.
Unknown whether he could make the bottom section springy enough
to effect a pushbutton spring.

 

[Kaz Kylheku]

On 2016-01-15, Gareth Magennis <sound.service@btconnect.com> wrote:

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

---


Thanks, might give that a go.

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.

 

[Jeff Liebermann]

On Fri, 15 Jan 2016 09:11:00 -0000, "Gareth Magennis"
<sound.service@btconnect.com> wrote:

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

Search for a rubber keypad repair kit:
<http://www.amazon.com/MG-Chemicals-8339-Rubber-Keypad/dp/B0081SGM8M>
<http://www.amazon.com/Keypad-Restore-Conductivity-Carbon-Copper/dp/B0026PRMVM>
<http://www.amazon.com/Caig-BCG327782-Caikote-44-Kit/dp/B00E1QYYC4>
<http://www.mcmelectronics.com/product/CAIG-LABORATORIES-K-CK44-G-/200-315>
<http://www.ebay.com/bhp/keypad-repair-kit>
<http://www.ebay.com/bhp/keypad-fix>
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
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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[Randy Day]

In article <n7aii3$idd$1@dont-email.me>, ham789@netzero.net says...

[snip]

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.
I never asked the price.
All his samples were rigid.
Unknown whether he could make the bottom section springy enough
to effect a pushbutton spring.

One of the guys at the makerspace brought
in some NinjaFlex 3D filament. It is quite
flexible, and a test cube was quite spongy.
I have no data on how durable it would be
in the OP's application, though.

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[whit3rd]

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?

 

[Jeff Liebermann]

On Thu, 14 Jan 2016 17:11:25 -0800, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
sound.service@btconnect.com> wrote:

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
http://www.devcon.com/products/products.cfm?family=Flexane%C2%AE%2094%20Liquid
http://www.amazon.com/Devcon-15250-Black-Flexane-Liquid/dp/B00065TLJK
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.

Oops. The Devcon Flexane 94 is probably too hard and stiff for your
rubber button that has to bend and act as a spring:
<http://oi65.tinypic.com/14xdmo3.jpg>
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:
<http://www.siliconeforbuilding.com/pdf/structuralglazing/Data_Sheet_SSG4000_UltraGlaze.pdf>
Argh... only 39.

These might help:
"Using Silicone Caulk as a Mold Material"
<http://forums.gardenweb.com/discussions/1472166/using-silicone-caulk-as-a-mold-material>

Durometer Hardness Scales:
<http://www.paramountind.com/pdfs/paramount_durometer_scale_guide.pdf>

MasterBond Adhesive hardness:
<http://www.masterbond.com/properties/hardness>


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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[Dave Platt]

In article <EI2my.44923$Wj7.3205@fx33.am4>,
Gareth Magennis <sound.service@btconnect.com> 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.