My alarm keypad has a few nearly-dead buttons and spares don't seem to
be available (it's a Karizma plus) so I need to either find another that
will work with the system or repair the original.
If there was no alternative I'd try to replace the "keys" with momentary
switches but I'd prefer to keep the membrane if possible.
Has anyone here successfully repaired membrane keypads? If so, how?

On Thu, 24 Oct 2019 10:44:28 +0100, wrote:

If there was no alternative I'd try to replace the "keys" with momentary
switches but I'd prefer to keep the membrane if possible.
Has anyone here successfully repaired membrane keypads? If so, how?

Why is the membrane failing? Breakup of the outer surface due to use
or just intermittent contact? For the latter you might be able to
open up the membrane and clean the contact faces.

See if there is suitably sized third party replacement. Assuming it's
a simple X/Y contact arrangement. Might have juggle connections
around to get the pinout correct.

--
Cheers
Dave.

On 24/10/2019 10:56, Dave Liquorice wrote:
On Thu, 24 Oct 2019 10:44:28 +0100, wrote:

If there was no alternative I'd try to replace the "keys" with momentary
switches but I'd prefer to keep the membrane if possible.
Has anyone here successfully repaired membrane keypads? If so, how?

Why is the membrane failing? Breakup of the outer surface due to use
or just intermittent contact? For the latter you might be able to
open up the membrane and clean the contact faces.

See if there is suitably sized third party replacement. Assuming it's
a simple X/Y contact arrangement. Might have juggle connections
around to get the pinout correct.


The problem is that some keys need very hard pressure or "jiggling" to
get a contact. When I've previously tried to fix similar things (TV
remotes) by cleaning the PCB it's always been a short term fix,
presumably because of a lack of conductive "stuff" remaining on the
membrane. I'd prefer to try a repair because of the printing on the
membrane and, as it's a common problem, I was hoping that someone here
might have found a long term fix.

wrote:
My alarm keypad has a few nearly-dead buttons and spares don't seem to
be available (it's a Karizma plus) so I need to either find another that
will work with the system or repair the original.
If there was no alternative I'd try to replace the "keys" with momentary
switches but I'd prefer to keep the membrane if possible.
Has anyone here successfully repaired membrane keypads? If so, how?

I've done it with conductive paint, but you'd have to somehow separate
the membrane if the contacts are in 'bubbles'.

What type is it. Type one two sheets of flexible pcb with a rubber or hard
button on top. Normally can be fixed by silver loaded paint if you can get
the layers apart without doing more damage.
2 blister ones where the top of the blister is conductive inside and shorts
connections underneath. Very hard to fix successfully since you can't get in
to them
3 The remote control type, bumpy pcb underneath, where the contact points
are higher and the bottom of the button coated in a conductive material.
These tend to dry out and turn to powder and this fills the gaps and either
shorts some keys out or stops what is left of the conductive button from
making a contact. In this case, disassemble Clean the pcb using an
ultrasonic cleaner bath to get the gunge out, and then see if you can get it
to work. In the end though the conductive material goes and you end up
having to glue ally foil to the buttons, which is both fiddly and can
eventually fall off.
I feel sure these makers could come up with a better solution than any of
these myself, even if its just a bit of springy phosphor bronze below the
keys, but I guess these other things are almost off the shelf solutions for
simple keypad designs.

I'm sure others will have their pet methods, but in the end a new assembly
might be better for something so crucial as an alarm where key repeats might
lock you out.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
wrote in message
...
My alarm keypad has a few nearly-dead buttons and spares don't seem to be
available (it's a Karizma plus) so I need to either find another that will
work with the system or repair the original.
If there was no alternative I'd try to replace the "keys" with momentary
switches but I'd prefer to keep the membrane if possible.
Has anyone here successfully repaired membrane keypads? If so, how?

On 24/10/2019 15:00, Brian Gaff wrote:
What type is it. Type one two sheets of flexible pcb with a rubber or hard
button on top. Normally can be fixed by silver loaded paint if you can get
the layers apart without doing more damage.
2 blister ones where the top of the blister is conductive inside and shorts
connections underneath. Very hard to fix successfully since you can't get in
to them
3 The remote control type, bumpy pcb underneath, where the contact points
are higher and the bottom of the button coated in a conductive material.
These tend to dry out and turn to powder and this fills the gaps and either
shorts some keys out or stops what is left of the conductive button from
making a contact. In this case, disassemble Clean the pcb using an
ultrasonic cleaner bath to get the gunge out, and then see if you can get it
to work. In the end though the conductive material goes and you end up
having to glue ally foil to the buttons, which is both fiddly and can
eventually fall off.
I feel sure these makers could come up with a better solution than any of
these myself, even if its just a bit of springy phosphor bronze below the
keys, but I guess these other things are almost off the shelf solutions for
simple keypad designs.

I'm sure others will have their pet methods, but in the end a new assembly
might be better for something so crucial as an alarm where key repeats might
lock you out.
Brian

I've assumed, from the feel, that it's the sort where a conductive area
on the bottom of the button bridges tracks on a PCB. I won't be able to
dismantle it for a few weeks but until then I might try changing the
codes to avoid the worn-out digits.

On 24/10/2019 10:44, wrote:
My alarm keypad has a few nearly-dead buttons and spares don't seem to
be available (it's a Karizma plus) so I need to either find another that
will work with the system or repair the original.
If there was no alternative I'd try to replace the "keys" with momentary
switches but I'd prefer to keep the membrane if possible.
Has anyone here successfully repaired membrane keypads? If so, how?

Might be of some use...

I repaired rubber PCB buttons on a crossword dictionary (like a
calculator only more keys) by gluing pieces of thin conductive plastic
on the worn previously conductive surfaces. The plastic was from a
black anti-static bag used for electronic components, and the glue was a
thin smear of RTV silicone.

It worked for a few years and probably still would but the owner snuffed it.

Cheers
--
Clive

On Thu, 24 Oct 2019 10:44:28 +0100, wrote:

Has anyone here successfully repaired membrane keypads? If so, how?

Yes...

I'm assuming silicone-rubbery membrane, black conductive spots press on parallel
tracks on circuit board? And you have cleaned the "rubber" and the pcb and it
was better but it needs lots of pressure because the conductive bit doesn't
conduct well?

I got a very small bag of conductive rubber spots and a tiny tube of special
glue, much like silicone sealant. Clean with acetone, shave off a bit of the old
rubber with a scalpel for clearance (which was probably unnecessary), stick on
the tiny very thin spot, job done. It's lasted very, very well.

(I have 97 rubber spots and a tube of dried hardened glue here, somewhere,
probably...)

I think this is the same item and a similar price:

REPLACEMENT Rubbers for Remote Controllers -Pack of:100 Conductive Rubber Pads
https://ebay.us/s16Ngv


Thomas Prufer

wrote in message
...
My alarm keypad has a few nearly-dead buttons and spares don't seem to be
available (it's a Karizma plus) so I need to either find another that will
work with the system or repair the original.
If there was no alternative I'd try to replace the "keys" with momentary
switches but I'd prefer to keep the membrane if possible.
Has anyone here successfully repaired membrane keypads? If so, how?

I did have a similar problem with a combined light/fan/heater
for bathrooms which just has remote, no switches at all. Found
that the problem was some gunk behind the keypad membrane.
Cleaned that off and it worked fine.

On Fri, 25 Oct 2019 08:28:53 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


I did have a similar problem

NOBODY has problems like you, you abnormal lonely cantankerous senile pest
who gets up EVERY NIGHT between 1 and 4 am in Australia, just troll and
pester people on Usenet!

--
Website (from 2007) dedicated to the 85-year-old trolling senile
cretin from Oz:
https://www.pcreview.co.uk/threads/r...d-faq.2973853/

On 24/10/2019 18:16, Thomas Prufer wrote:
On Thu, 24 Oct 2019 10:44:28 +0100, wrote:

Has anyone here successfully repaired membrane keypads? If so, how?

Yes...

I'm assuming silicone-rubbery membrane, black conductive spots press on parallel
tracks on circuit board? And you have cleaned the "rubber" and the pcb and it
was better but it needs lots of pressure because the conductive bit doesn't
conduct well?

I got a very small bag of conductive rubber spots and a tiny tube of special
glue, much like silicone sealant. Clean with acetone, shave off a bit of the old
rubber with a scalpel for clearance (which was probably unnecessary), stick on
the tiny very thin spot, job done. It's lasted very, very well.

(I have 97 rubber spots and a tube of dried hardened glue here, somewhere,
probably...)

I think this is the same item and a similar price:

REPLACEMENT Rubbers for Remote Controllers -Pack of:100 Conductive Rubber Pads
https://ebay.us/s16Ngv


Thomas Prufer

Vielen Dank, Thomas. That's exactly what I was looking for but didn't
know existed.