Those Pesky Membrane Switches

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fine-tune
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Those Pesky Membrane Switches

Post by fine-tune »

My favorite bench style DMM was manufactured by B&K Precision. This instrument had
every feature I wanted and when all the switches began to fail it was depressing. I asked
a service company to estimate the cost of repair. It was more than I had paid for the thing,
so I did the job myself. It was hours of very unpleasant work! After that, I junked most
devices that had failing switches.

I've got three identical TV remotes that I like a lot. Only one is still functioning and this model
is no longer manufactured. As usual, those mushy membrane switches are the problem.
I remember an article years ago in Popular or Radio Electronics about using aluminum foil to
repair this type of switch. I tried it, got frustrated, and tossed the gizmo in the trash. Are
there reliable techniques that actually work most of the time?
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dacflyer
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Re: Those Pesky Membrane Switches

Post by dacflyer »

are you talking about them silicone keys ?
i had a cordless phone that i had to take apart once in a while to wash the silicone pad, it seems it oozes some kind of oil like substance and then the pads won't make contact any more. but once i washed it and the circuit board, let it dry, then it was good for about another 6 months.
but ya, then silicone pads suck,, and whats worse are them metal disk switches, like you see used on some old calculators or a bunch of them remotes for the X10 units..
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Janitor Tzap
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Re: Those Pesky Membrane Switches

Post by Janitor Tzap »

Hah.......

Another victim of the rubber carbon buttons. :(

If you do a search of this forum you'll find several postings on the carbon button calamity.

Note:
The "Tin Foil Fix" only works if the contact area on the PCB is Copper, or Silver traces.
Carbon coated contact areas will wear carbon off on to the Tin Foil, and eventually building up a layer of carbon on it.
Which effectively increases the resistance, and stopping the switch from conducting.


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haklesup
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Re: Those Pesky Membrane Switches

Post by haklesup »

"when all the switches began to fail it was depressing"

Or not Depressing [the switch] as the case may have been :)

There were a range of button technologies and many were not reliable in the long term. Typically the rubber contacts would oxidize or otherwise loose surface conductivity over time and start to get too hard to push. The older metal contacts would punch through the CPB metal and go open for example. As you have seen, repairing them is generally not worth the effort especially if the failure mechanism is change of material properties over time, its something non mechanical in many cases.
fine-tune
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Re: Those Pesky Membrane Switches

Post by fine-tune »

I googled "membrane switch" and there are a million images.

Anything soft and mushy reminds me of a membrane, but I guess the strict technical
definition does not include those silicone keys on a TV remote.

Normally, I would never consider repairing a TV remote. The three units I've got are
kind of unique, and are very easy to use in a completely darkened room. I was surprised
when they were suddenly discontinued.

The remote that stilll works is used in my bedroom. I'll have to find a subtitute before it
poops out like the other two. Maybe I'll pry one of the dead units open and clean the
contacts.
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Janitor Tzap
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Re: Those Pesky Membrane Switches

Post by Janitor Tzap »

fine-tune wrote:Normally, I would never consider repairing a TV remote. The three units I've got are
kind of unique, and are very easy to use in a completely darkened room. I was surprised
when they were suddenly discontinued.
I'm not. :x
We live in a consumer driven, throw away society.
Manufacturers have come too realize that if their products last more than 2 - 3 years.
The consumer won't purchase they're so called latest, and greatest product,
if the consumer is still using an older working product.
It use too be that the reason you replaced your old item was because the new item was easier to use.
Or had more, and better features.
fine-tune wrote:The remote that stilll works is used in my bedroom. I'll have to find a substitute before it
poops out like the other two. Maybe I'll pry one of the dead units open and clean the
contacts.
Good idea. :)
But also check the battery connections, and solder joints in general.
If you have dropped these remotes several times.
It is a good bet that you have loosened some of the connections up. :wink:


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haklesup
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Re: Those Pesky Membrane Switches

Post by haklesup »

"Manufacturers have come too realize that if their products last more than 2 - 3 years.
The consumer won't purchase they're so called latest, and greatest product, "

I think there is more to it than that, especially for remotes where its the TV not the remote that is usually the profit driver. In many cases especially for things with plastic cases, the manufacturer makes enough for the required sales projections or until the mold wears out. However you get there, within 2-3 years of a production run you may have trouble sourcing the mold, any of the components or meeting min manufacturing quantities. At that point, you just respin the design. For remotes at least, there is a lot of cross compatibility and universal solutions in every price range. Cost should not be a barrier to turning on the TV remotely. Lots of great smart phone remote apps if you have one with an IR emitter.

Personally I try to be an Owner not just a Consumer but things do wear out and new stuff comes along that really is better.
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Casey1947
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Re: Those Pesky Membrane Switches

Post by Casey1947 »

Hello,

Back in the late 60's I bought my wife a new electronic timer with push buttons. She really liked it because she was young and followed recipeis very closely. Around 20 years later one of the buttons quit working. Since there were three timers I told her just to use one of the other two. A year or so later another button quit working. She then noticed that if you shook it you could hear something sliding around. I got out my trusty old philips screwdriver and dissasembled. (only two screws and neighter one was hidden) Inside were three curved gold plated pieces of spring stock which origionally were held in place with Scotch tape. I used fingernail polish remover to clean the old yellow tape off and applied new
scotch tape. I re-assembled the timer, put in new batteries and it is still working 45 years later.

Casey
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