25 Apr
2018
25 Apr
'18
12:45 p.m.
Gentlepeople,
I have a Philips logic analyzer (PM3585) which is about 20 years old at this point. It
seems to be basically functional except for the keyboard, which unfortunately is a
critical part.
This is one of those molded rubber type, with a circuit board behind the rubber that has
contact areas made of carbon film (at least they are black in color) and on the back of
each key a small cylindrical bump also coated with carbon. Some of the buttons work but
most don't seem to even if I press hard.
I've disassembled the keyboard, which was easy enough. Inspection shows no damage and
no signs of corrosion or contamination. I wiped everything with isopropyl alcohol anyway.
The result is no change in behavior.
Any suggestions for what to do next?
paul
25 Apr
25 Apr
2:16 p.m.
I have a Philips logic analyzer (PM3585) which is about 20 years old at this point. It
seems to be basically functional except for the keyboard, which unfortunately is a
critical part.
This is one of those molded rubber type, with a circuit board behind the rubber that has
contact areas made of carbon film (at least they are black in color) and on the back of
each key a small cylindrical bump also coated with carbon. Some of the buttons work but
most don't seem to even if I press hard.
I've disassembled the keyboard, which was easy enough. Inspection shows no damage
and no signs of corrosion or contamination. I wiped everything with isopropyl alcohol
anyway. The result is no change in behavior.
Any suggestions for what to do next?
I had a similar problem with an old VCR remote control. The problem seemed
to be that the bumps on the back of the keys lost their conductivity (and
cleaning them made them worse).
My solution was to glue pieces of aluminium foil to the back of the keys.
It was tedious but it seemed to sort it out.
Regards,
Peter Coghlan.
paul
26 Apr
26 Apr
9:32 a.m.
Easier solution is to apply some conductive light lube. Radio Shack used to
carry it, and I repaired a LOT of remote controls with it!
Cindy
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Peter
Coghlan via cctalk
Sent: Wednesday, April 25, 2018 4:17 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Restoring rubber keyboard on a logic analyzer
I have a Philips logic analyzer (PM3585) which is about 20 years old at
this point.
It seems to be basically functional except for the keyboard,
which unfortunately is a critical part.
This is one of those molded rubber type, with a circuit board behind the
rubber
that has contact areas made of carbon film (at least they are black
in color) and on the back of each key a small cylindrical bump also coated
with carbon. Some of the buttons work but most don't seem to even if I press
hard.
I've disassembled the keyboard, which was easy enough. Inspection shows
no
damage and no signs of corrosion or contamination. I wiped everything
with isopropyl alcohol anyway. The result is no change in behavior.
Any suggestions for what to do next?
I had a similar problem with an old VCR remote control. The problem seemed
to be that the bumps on the back of the keys lost their conductivity (and
cleaning them made them worse).
My solution was to glue pieces of aluminium foil to the back of the keys.
It was tedious but it seemed to sort it out.
Regards,
Peter Coghlan.
paul
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29 Apr
29 Apr
10:28 a.m.
On Apr 26, 2018, at 12:32 PM, Electronics Plus via
cctalk <cctalk at classiccmp.org> wrote:
Easier solution is to apply some conductive light lube. Radio Shack used to
carry it, and I repaired a LOT of remote controls with it!
Cindy
I made a successful repair. Here are the steps I used:
As I mentioned, I tried cleaning with isopropyl alcohol, without much success.
I realized that I could test the rubber contact points with a multimeter, probing two
spots on the surface. The offending keys had much higher resistance or simply tested
open. That made it easier to try other options without having to assemble/disassemble
each time.
I found a spray can of "contact cleaner/lubricant" and tried that. OOPS. Made
it much worse. Looked at the ingredients: one is "mineral oil". Ok, so
that's fine for metal wiping contacts I suppose, but not for this. Washed the keypad
thoroughly with dishwashing soap and water, then wiped several times with alcohol, that
got me back to where I was.
Then I realized I still have a tube of powdered graphite (the stuff sometimes used for
lubricating locks, though it turns out that's not a good idea. Squirted some onto a
Q-tip and rubbed the bad contact pads with that. They look shiny as a result rather than
dull black. But it works!
So that's the answer: graphite powder. I now have a working analyzer again. It will
be interesting to see if the graphite wears off eventually, I suppose it might but
that's ok, I can just do it again.
Thanks everyone for the suggestions.
paul
3:29 p.m.
On Sun, 29 Apr 2018, Paul Koning via cctalk wrote:
So that's the answer: graphite powder. I now have
a working analyzer
again. It will be interesting to see if the graphite wears off
eventually, I suppose it might but that's ok, I can just do it again.
Many years ago I used graphite obtained from a soft pencil to revive
rubber keyboard pads and from my observation it wore rather quickly, in
particular moving to the surface contact was made against. I wonder if
there is a non-industrial way to make graphite stay in place on rubber.
Maciej
8:44 p.m.
On Sun, Apr 29, 2018 at 11:29 PM, Maciej W. Rozycki via cctalk
<cctalk at classiccmp.org> wrote:
On Sun, 29 Apr 2018, Paul Koning via cctalk wrote:
It's not cheap (and IIRC you have to use the whole lot in one go), but
Chemtronics make a kit to repair such keypads. Possibly worth it for
a useful instrument though.
In the UK you can get it here :
https://uk.rs-online.com/web/p/conductive-adhesives/3888673/
and I guess it's also available across the Pond.
-tony
So that's the answer: graphite powder. I now
have a working analyzer
again. It will be interesting to see if the graphite wears off
eventually, I suppose it might but that's ok, I can just do it again.
Many years ago I used graphite obtained from a soft pencil to revive
rubber keyboard pads and from my observation it wore rather quickly, in
particular moving to the surface contact was made against. I wonder if
there is a non-industrial way to make graphite stay in place on rubber.
Maciej
8:58 p.m.
On Mon, 30 Apr 2018, Tony Duell via cctalk wrote:
In the UK you can get it here :
https://uk.rs-online.com/web/p/conductive-adhesives/3888673/
and I guess it's also available across the Pond.
Silly thought:
Half a century ago, there used to be a conductive glue that was peddled
to the general [not even owning a soldering iron] public as heat-less
solder.
If that's still available in any form, would that work?
There is some stuff that claims to be a conductive paint:
https://www.amazon.com/Bare-Conductive-BarePaint-Paint/dp/B076BSBMK6
9:37 p.m.
Answered my own question. The repair stuff is called "Aquadag E":
https://semicro.org/products/carbon-paint-conductive
https://www.ebay.com/itm/AQUADAG-CARBON-PAINT-ARCADE-MONITOR-TV-CRT-CATHODE…
Should work a treat in this application.
--Chuck
9:29 p.m.
On 04/29/2018 08:44 PM, Tony Duell via cctalk wrote:
It's not cheap (and IIRC you have to use the whole
lot in one go), but
Chemtronics make a kit to repair such keypads. Possibly worth it for
a useful instrument though.
In the UK you can get it here :
https://uk.rs-online.com/web/p/conductive-adhesives/3888673/
and I guess it's also available across the Pond.
Does anyone still make aquadag?
--Chuck
2 May
2 May
11:02 a.m.
On Apr 29, 2018, at 11:44 PM, Tony Duell via cctalk
<cctalk at classiccmp.org> wrote:
...
It's not cheap (and IIRC you have to use the whole lot in one go), but
Chemtronics make a kit to repair such keypads. Possibly worth it for
a useful instrument though.
In the UK you can get it here :
https://uk.rs-online.com/web/p/conductive-adhesives/3888673/
and I guess it's also available across the Pond.
-tony
It is, and for less money. The various electronic and industrial supply outlets carry it,
for example Newark, Digikey, and MSC Direct. Digikey sells it for $23, that's
significantly better than 23 pounds...
The Aquadag approach looks interesting, but that may not be as reliable. That seems to be
a conductive coating intended for rigid objects like CRTs, as opposed to a substance
intended to repair rubber keypads.
So if my graphite cure doesn't last, it sounds like the Chemtronics products is the
next answer.
Thanks!
paul
11:34 a.m.
http://tabalabs.com.br/videogames/atari/controle_5200/ - that is how I
solved this problem
2018-05-02 15:02 GMT-03:00 Paul Koning via cctalk <cctalk at classiccmp.org>:
On Apr 29, 2018, at 11:44 PM, Tony Duell via
cctalk <
cctalk at classiccmp.org> wrote:
...
It's not cheap (and IIRC you have to use the whole lot in one go), but
Chemtronics make a kit to repair such keypads. Possibly worth it for
a useful instrument though.
In the UK you can get it here :
https://uk.rs-online.com/web/p/conductive-adhesives/3888673/
and I guess it's also available across the Pond.
-tony
It is, and for less money. The various electronic and industrial supply
outlets carry it, for example Newark, Digikey, and MSC Direct. Digikey
sells it for $23, that's significantly better than 23 pounds...
The Aquadag approach looks interesting, but that may not be as reliable.
That seems to be a conductive coating intended for rigid objects like CRTs,
as opposed to a substance intended to repair rubber keypads.
So if my graphite cure doesn't last, it sounds like the Chemtronics
products is the next answer.
Thanks!
paul
2426
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