Worn carbon contacts on a keyboard..

[Neal]

Forgive me if this topic has been covered... a quick search didn't turn up anything.
I've got a keyboard here that has the carbon buttons or dots with rubber covers for key contacts. The carbon buttons on the circuit board on some of the keys are pretty worn. Is there a conductive paint or coating I can put on these buttons to restore them?
Thanks, Gents!

[Mick Bailey]

There are a number of ways of doing this, but none as good as replacing the strip. Actually, while the keyboard is apart I usually replace all of them. Only if the contact strips are no longer available do I repair them. There are a few companies that sell thin carbon-polymer dots that can be glued over the damaged area. Also, I've removed the old ones with a scalpel and bonded new ones on taken from a donor strip. It's sometimes difficult to get the velocity sensitivity evened out when you do this. Any discrepancy in height affects the velocity calculation, which is derived from the time taken from the 1st contact making, to the 2nd one (if you have a velocity-sensitive keyboard).

You may be surprised at how relatively inexpensive the strips can be, especially from Roland.

I've just re-read your post and you say the PCB has carbon pads - can you post a picture of how worn they are? Sometimes conductive paint can be used to restore them, but it depends on how much the keyboard is used. I haven't had much long-term success with pro keyboards.

[Jazz P Bass]

Number 1 on the carbon dots is 'do nothing'.
They do not like being touched (finger skin oil).
The 'liquid carbon' applications are a mess to work with.
If they are bad, then they are bad.

The PCB can be cleaned by lightly rubbing the area with a pencil eraser.

[soundguruman]

1. Loosen the hold down screws.
2. slide the carbon contacts over, maybe 1/8 inch or less.
3. Tighten it back down.
Usually does the trick, just move the contact point over "a hair."

Not liquid carbon. No.
Coat the surfaces with Caig Deoxit G-100. That maximizes the contact surface conductivity.
No, "ordinary contact cleaner" does not work even a fraction as well. You gotta use the GOOD stuff.

[Mick Bailey]

The PCB can be cleaned by lightly rubbing the area with a pencil eraser.

He says they're carbon pads on the PCB. If they're worn any further cleaning isn't going to hold. With the gold contacts I just wipe them with 100% propanol to remove any dust created by the worn contact pad. Worn carbon contacts on a PCB will just about hold up with a superficial repair to give a domestic keyboard a few more months of life.

[soundguruman]

He says they're carbon pads on the PCB. If they're worn any further cleaning isn't going to hold. With the gold contacts I just wipe them with 100% propanol to remove any dust created by the worn contact pad. Worn carbon contacts on a PCB will just about hold up with a superficial repair to give a domestic keyboard a few more months of life.

So, move the circuit board over a bit, it may work again.

Depends on what they are cleaned with.

Certain cleaners work far better than others. They enhance conductivity.

These cleaners cost a lot. Most people won't use them.
But there is an advantage to using the better cleaners.
These can work, and keep working, where others fail.

Propanol cleans the surface.
But it does nothing to enhance conductivity, over a long period of time.

Other cleaners will enhance conductivity. And keep working longer, much longer.

BUT do you want to spend $30 on one ounce of cleaner?
sometimes, it's worth it.

[Mick Bailey]

I've never seen a single pro keyboard that doesn't have a positive location method between the PCB and key strips, so moving the relationship isn't possible - at least not for any of the keyboards I've ever worked on. From a manufacturing point it would introduce an extra step in aligning the assembly. Even if you could do this, the wear pattern on the dot is often on either side - sometimes right through to the silicone. So if you moved them, the problem would be worse as you'd widen the gap between one of the static contact pairs and the worn side of the dot. You'd also lose contact with those keys that were previously marginal.

What models of keyboard can you do this with?

No amount of contact cleaner will replace missing carbon-elastomer. Replacement costs so little compared to (say) re-tubing an amp that it doesn't make sense to send a serious or pro player away with anything less than perfect. A £1500 keyboard can have a complete new contact set for the price of a pair of 6L6GCs. When I factor in the time to strip the keyboard I don't want to see it coming back again.

With Rolands it also gives the opportunity to replace the old grey strips with the much better green ones. So an upgrade and repair at the same time.

[Enzo]

We need to find out what the keyboard is if we want to continue. Rubber contacts may not be expensive, but for older boards they may no longer be available. The contacts on a Poly 6 are not to be found, price is not the objection. There are Yamaha weighted keyboards with no longer available contact stripes.

[diydidi]

With Rolands it also gives the opportunity to replace the old grey strips with the much better green ones. So an upgrade and repair at the same time.
I like it!!!!!!!!
Mick is right on.
Those conductive paints work, but are messy to work with, and it is only a temporary solution.

[Mick Bailey]

Rubber contacts may not be expensive, but for older boards they may no longer be available.

That's why I mentioned repair options in post #2. People look to repair first and often never even enquire with the manufacturer if parts are available. A keyboard I worked on last year had repairs all over the place and the poor guy had been charged £230. Within three weeks it was acting up again. It was an old keyboard, but there was still stock in Japan so they had them shipped to me. Total cost for the entire keyboard? £32 - including shipping.

[Neal]

Guys, I sincerely appreciate all the responses. This site, and the expertise offered, is truly invaluable for those of us trying to get through the next gig. Thank you.
The keyboard is an old Roland W-30. Expensive in its day, obsolete now. I'd almost forgotten I had it stored away, and dug it out so the kids could mess with it. When I plugged it in, I was surprised that it actually loaded the operating system.
I'll give it a thorough cleaning, and I've already got Deoxit. I may get lucky.
Thanks again, gents!

[Mick Bailey]

The contacts strips were still available from Roland quite recently for this keyboard, though the last ones I bought had a different part number (they also fitted something else). Here in the UK Roland parts guys are superb and know what-fits-what. They even hooked me up with some Space Echo parts that hadn't been stocked by themselves for over 18 years.

Raise a job ticket and they'll give you a price if you need any.

[Mark Hammer]

I have restored a number of TV remotes that also use conductive rubber and carbon pads, using this stuff: http://www.stabilant.com/

...which is normally hard to find but can be gotten through on-line retailers (e.g., http://www.amazon.ca/Stabilant-5ml-K.../dp/B001E50GQS )

Not cheap, but a little bit will last you a long time. There are limits to the miracles it can perform, but within those limits it IS miraculous. And the nice thing is that, unlike conductive paint, you don't have to be scrupulously precise about applying it.

This is NOT a cleaner. It is a contact enhancer that functions like a thin layer of liquid solder.

[Mick Bailey]

It's the only thing I've found that will properly restore the carbon-wiper Clarostat pots where even Deoxit won't work.

You do need a contact to begin with though, many of the severely worn keyboards I see don't have anything left. It's superb on camera contacts.

[Mark Hammer]

Yup. What makes it so miraculous (it stays in a stable viscous state for the life of the product), also constrains how miraculous it can be. You can not build up layers, so if the connectivity gap is greater than the thickness of the layer formed, you're SOL. But still, there are one heckuva lot of things that fall within those constraints.