Microwave oven membrane keypad repair

[jonpaul]

Hello,   used Sharp Carousel microwaves 1200W since 1999,

Had three  fail with bad membrane touch keypad, the type that is part of the front surface, the keys stop responding, or need repeated hard manipulation.

Replacement keypads or finding another exact white color, and fit seems impossible.

Has anyone disassemble the microwave, and be able to clean of fix these terrible membrane keypads?

Many thanks

Jon

[coppercone2]

is it a carbon backed rubber or a metal semisphere switch ? is it on a FR4 or a flex circuit ?

If its disintegrated carbon, I Don't know how to deal with that, probobly glue. If its a semisphere switch (popular now) you can get replacement parts from keystone etc and flush it with alcohol or contact cleaner. If the carbon rubber is just dirty you can wipe it with contact cleaner (not sure if alcohol is a good idea on the rubber).

[sokoloff]

I think they're impractical to attempt to repair.

I'd have no problem living with a black keypad (or imperfect match white) on a white microwave and would try to chase the part.

Something like whichever of these is the right match for your [unspecified] model:
https://www.repairclinic.com/PartDetail/Touchpad/FUNTKB247MRE0/1913778
https://www.repairclinic.com/PartDetail/Touchpad/FUNTKB368MRE0/1913791

[coppercone2]

that one is like a fluke scopemeter, its silver ink traces on a flexible material that is not kapton and also carbon on the back of the keys.

That kind has the traces break. You might be able to fix that kind of keypad with conductive ink pen. I had so many failures in my scope meter I bought a replacement PCB because there was too many cracks to fix.

[jonpaul]

CopperCone and Sokoloff: Many thanks for   fast tips!

Perhaps caused by may daily uses, with steamer creating a lot of water vapor.

I still Have to disassemble and see the type of kbd, membrane and search for spare parts.

 I hope that either   cleaning or conductive pen is a good solution.

Jon

[coppercone2]

you can also cut carbon off of something else and glue it to the inside of the other pad with some careful surgery to make the look the same, since the exterior won't change in that case

[james_s]

I recently completed a project repairing a membrane keypad on a veterinary incubator. The unit was old and the the company that made it is no longer in business so no parts available. A replacement machine was $10k so it was worth some effort to repair. The original flex had gotten animal pee on it which rotted off some of the conductive printing which was between two layers and I was not successful in finding a way to repair that.

Anyway what I ended up doing is carefully peeling the overlay off of the keypad and then I laid out a PCB copying the button positions and wiring of the original printed flex. I had the board made on 0.6mm FR4 and then taped new snap disc buttons over it then bonded the original overlay onto my new board. It came out really nicely and works perfectly. The PCB I made is actually a bit thinner than the original printed flex. There are both buttons and SMT LEDs on it and on the back I used a surface mount 0.1" inline pin header in place of the original which had a cable that was part of the flexible PCB that made up the whole thing.

In my case the membrane keypad was stuck to a painted steel panel which had stuff behind it so there was no room to install pushbuttons in the panel. You could try something like this for your microwave, or you could do something fun and make a new control panel using nice clicky industrial buttons or something if you have room behind the panel. Is it worth the effort? Well not if you're billing for your time, but as a hobby project it sounds like fun.

[TERRA Operative]

If you don't care about the whole membrane thing, some clicky keys and keycaps like the custom keyboard guys use could make for a unique and very satisfying replacement keyboard.