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 14th 16, 11:01 PM posted to sci.electronics.repair
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Default Key contact restoration

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 15th 16, 01:11 AM posted to sci.electronics.repair
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Default Key contact restoration

On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
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
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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Old January 15th 16, 01:28 AM posted to sci.electronics.repair
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Default Key contact restoration

On Thu, 14 Jan 2016 17:11:25 -0800, Jeff Liebermann
wrote:

On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
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
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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Old January 15th 16, 02:56 AM posted to sci.electronics.repair
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Default Key contact restoration

On 2016-01-15, Jeff Liebermann wrote:
On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
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!
  #5   Report Post  
Old January 15th 16, 03:24 AM posted to sci.electronics.repair
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Default Key contact restoration

On 15/01/16 12:11, Jeff Liebermann wrote:
On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
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.



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Old January 15th 16, 03:56 AM posted to sci.electronics.repair
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Default Key contact restoration

On Fri, 15 Jan 2016 02:56:51 +0000 (UTC), Kaz Kylheku
wrote:

On 2016-01-15, Jeff Liebermann wrote:
On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
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=p roduction&language=1&format=16&CFID=11369918&CFTOK EN=1c713f7731a98b98-A229D917-9DA3-18D9-6BC94692623356A2
At 10-20% of solution by weight, it's not going to be very potent.


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

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

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Old January 15th 16, 08:24 AM posted to sci.electronics.repair
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Posts: 5,186
Default Key contact restoration

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?

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Old January 15th 16, 08:29 AM posted to sci.electronics.repair
MJC MJC is offline
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First recorded activity by DIYBanter: Aug 2015
Posts: 139
Default Key contact restoration

In article ,
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.
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Old January 15th 16, 08:55 AM posted to sci.electronics.repair
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First recorded activity by DIYBanter: Oct 2012
Posts: 1,243
Default Key contact restoration

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-interfac...rey/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.
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Old January 15th 16, 09:11 AM posted to sci.electronics.repair
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Posts: 817
Default Key contact restoration



"Jeff Liebermann" wrote in message
...

On Thu, 14 Jan 2016 23:01:20 -0000, "Gareth Magennis"
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
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.



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