Repair Keyboard Rubber Contacts?

[Bouncy nugget]

Hey, new here! Don't really know technical terms but here goes! (skip to end for actual question)

I have a digital piano that has some malfunctioning keys. I took it apart to see what was happening as i have been told it is usually dirt and dust under the rubber contacts that causes it. The first thing i noticed was grease had leaked under the contacts so i initially thought that was the problem. So i wiped it down thinking i would clean the grease off, but the keys still didn't work right.

When i wiped the sensor down i wiped down a section of the chip board thing and i noticed they got darker in colour than the neighbouring sensors and all the notes i had wiped stopped working correctly also. I thought i had just spread the grease. So i washed the sensors down with alcohol cleaner. Made no difference.

Eventually i thought maybe i would try mess a note up on purpose. So i took the contacts off a section of the keyboard that was working and rubbed my finger on just one note. The one note sensor started malfunction. I think at this point i started thinking i didn't spread the grease but rather i had wiped something off that i shouldn't have.

QUESTION: So i think i rubbed off some kind of conductive powder or something from the board that the rubber contacts make contact with so the effected notes don't trigger correctly. I don't know how these electronic things work but i'd like to get it fixed ASAP. Does anyone know what it is i need to do?

EDIT: To be more specific the rubber contact is a "tri-sensor" from the Casio Privia keyboard range so the rubber contact is like a 3 in 1 thing. The thing on the chip board that the contacts press on has these black lines that run under each of the contact points and these black lines are sort of in a S kind of shape (they're connected to each other). When i press the busted notes with too much pressure on the key in the area above the sensor the note cuts off, and then when i release the note it triggers another note at full velocity. Hope that all made sense

 

[shrtrnd]

Can you post a picture of what you're seeing?

 

[Bouncy nugget]

So here you can see the rubber contacts on the left and the sensors thingies beneath them. The black stuff on that board beneath the contacts is what i rubbed down and as i did it and the black parts darkened it looked as though they were getting covered in grease (wetness).

After i tested it by rubbing a working note with my finger (which i don't think had grease on it) it also looked as though i had wet (wet isn't the right word here) it a bit, but i think i actually just removed a coating of something. It visually sort of looked like i had wiped dust off the surface but i don't think it was dust.

I think the problem may have initially started out with grease leaking under the notes and cutting off contact though.

 

[Bouncy nugget]

Like essentially i'm saying i think i rubbed off some kind of conductive powder and now the rubber contacts don't work like they should. I need someone who knows this stuff to tell me though?

 

[Harald Kapp]

You can buy repair kits for this specific purpose. Or a keypad fix fluid/gel that replaces the worn off conductive surface of the old keyboard.

 

[shrtrnd]

Typically, the 'conductive powder' you wiped-off, is carbon from the carbon disc on the rubber push-button itself.
Contact is made between the sqwiggly lines on the printed circuit board, by the carbon disc on the bottom of the
push-button.
Usually, your failure is due to the carbon disc deteriorating so much that it no longer provides a conductive path
when the push-button is depressed and doesn't have enough carbon material left to make the connection between
the sqwiggly lines on the PCB.
If you tried cleaning the carbon discs on the push-button bottoms and the connection isn't being made, there's just
not enough of that carbon disc to make the connection.
You should try Harald Kapp's advise on repair kits.
Good luck, it's kind of time consuming, but that is what's needed to fix this.

 

[Bouncy nugget]

You can buy repair kits for this specific purpose. Or a keypad fix fluid/gel that replaces the worn off conductive surface of the old keyboard.

Yeah i've been reading up and it seems that way. Does it have to be anything in particular?

Either way i read that if you scribble some B pencil on the carbon contacts it may work again, so i tried it out and it actually worked looll. For future reference though when these silly pencil fixed contacts stop working again is it okay to put the gel over the lead or will i have to somehow clean the smudged pencil off first before adding the gel?

 

[Harald Kapp]

I have never used that used so far. I'd expect this to be explained in the user insctructions of the specific material you buy.
Cleaning is probably required to prepare the surface for good adhesion. Otherwise the fluid will adhere to the pencil remains and flake off together with these.

 

[Bouncy nugget]

Can it just be any kind of conductive gel? Nothing specifically made for contact rubbers on keyboards or anything like that?

 

[Harald Kapp]

It needs to stick to the rubber mat, it needs to dry so it doesn't stick to the pcb contacts, it needs to have sufficient conductivity.

Gold foil used for leaf guilding may be suitable, albeit a tad more expensive

If you find some othe stuff that fulfills these criteria, give it a try - no warranty from my side.

 

[Bouncy nugget]

find some othe stuff that fulfills these criteria, give it a try - no warranty from my side.

Haha, well that should be enough information.

Cheers mates!

 

[Bouncy nugget]

Actually i have another question. I just want to know specifically where i should spread the conductive gel? Should i cover very precisely all the black carbon material? Or can i just cover the whole thing recklessly? Or is it the little interlaced section that needs to be covered?

I have no idea

 

[Harald Kapp]

Use the gel only where previously conductive material has been. Otherwise you risk unpredictable behavior when pressing multiple keys. It will also save on the "precious" material.

 

[Bouncy nugget]

Use the gel only where previously conductive material has been. Otherwise you risk unpredictable behavior when pressing multiple keys. It will also save on the "precious" material.

I'm not actually sure where it was because it wasn't really noticeable until it was rubbed off.

But say how the carbon material is an E type structure, would it be bad if i spread the gel across the horizontal lines? Should i draw neatly over the E? Or is it okay to draw a nice big rectangle over the entire E straight up and down, but obviously not connecting the carbon material of one not to another note?

 

[Harald Kapp]

The carbon, gel, whatever should be where I made the red marks:

Thus the carbon, gel, whatever on the silicone mat will create a contact between the two fingers on the PCB when the button is pressed.

 

[Bouncy nugget]

So on the interlaced section of the contact material? Sorry, just trying to be really specific so i don't get it wrong.

 

[Harald Kapp]

So on the interlaced section of the contact material?

not on the contact side (interlaced fingers), on the silicon mat. Such that when pressed the mat makes contact with the interlaced fingers and the new conductive surface of the mat closes the contact between the fingers.
If you put the contact material directly onto the fingers, it will create a permanent contact, thus negating the function of the silicon keyboard mat.

 

[Bouncy nugget]

Oh right, Cheers!

 

[Bouncy nugget]

Hello to anyone who will see this. I purchased a conductive silver pen and put some of this onto the rubber contacts but it hasn't made a difference. I believe the problem is the black stuff on the circuit board that these rubber contacts press on. I don't know what substance it is that i need to apply to the board though. I've been scribbling lead pencil on the circuit board which fixes it temporarily but eventually wears off. I'm hoping for a permanent solution.

Please advise!

 

[shrtrnd]

Have you tried contacting the manufacturer and inquiring about buying a replacement keypad?