Advice needed on membrane contact board cleaning

I'm refurbishing a Studiologic controller. I've cleaned and serviced every optical part of the keyboard but think I should make it a complete servicing. I get on occasion an slightly erratic velocity response from just a few keys and the membrane contact cups are all clear of contamination up top so it might be under the membrane. One slightly erratic response comes from Bflat below middle C and the contact board is sectioned into upper and lower at that point so something could have worked its way in. Any advice of how to best approach this sensitive procedure.

PS. I've already built a new wooden chassis with custom end blocks and removable key slip so lifting a key out will not require anything other than first removing the tension spring and pressing on the key retaining plastic nib. Damn that design of rigid key slip for hammer controllers!!!!!!I won't be taking this particular Fatar on bookings so adding the weight of a wooden chassis wasn't a concern. I have lighter controllers for offsite piano bookings.

Those membrane type contacts are very common in all kinds of contact switches incliding keyboards, remote controlls etc.

The contact imbeded in the rubber is a simple carbon type contact. The board usually uses a simular carbon or gold contact. I suggest you use straight Isopropyl alcohol only, 100%, bot the drug store stuff thats 50% water.

you do not want to use anything tjhat leaves a residue, removed the carbon contacts, or damaged the rubber. If you use something petroleum bases you'll wipe it out.

Typical contact cleaners may have silicon lubricants that may work good in the short term but thay will attract dust and make the problem worse, plus they can damage the rubber by warping it up.

Be sure to use a lint free cloth as well. Any lint left behind will cause intermittant or dead contacts.

I would like to hear about anything that will work on those things also. My experience has been that once they start to become erratic the end is usually near. I had some luck cleaning up some of the early ones; microwave panels, Japanese made phones, etc., but in the last ten years or so most of the Chinese made stuff I've had just quits shortly after the pads start to get flakey.

edit: I've tried Isopropyl, but probably not 100%. You can usually find 70% at a drug store if you look.

Are you saying it's different across the length of the keyboard. That seems odd. I'd think it would be uniform across. Is it possible that the membrane is warped or worn there and the contacts aren't finding each other as they should? Seems likely as that position probably sees the most usage.

Oh, and I second WRG's alcohol recommendation. Handle the membranes delicately. You don't want to stretch or deform it.

I used to have a supply of foam tipped qtips. They were great because you could get in and clean without leaving fibers behind and make detail work like this super easy. You may want to track something like that down because I doubt this will be last time you clean that thing.

May as well get a small can of 100% at the hardware store. It's fairly cheap and a small jug will last a while and has all kinds of usages around the house/workshop. It's usually near the paint supplies.

I've cleand my remote controll at least 10 times now. It went a year new and it seems to go 6 months between cleanings now.

I used to repair all kinds of computer, calculator, and industrial type keyboards and they are basically all the same deal. The worst ones stainless steel disks that would bend to make a contact. They would cut into the traces and loose contact. Thoser required using super fine emory cloth to smooth the traces down. Crappy design. I've also seen magnetic reed switches which were the best, then all kinds of momentary switches.

The layererd film suffers from distortion but the cleaning process is the same as the rubber type. Once they distort to the point where they make a constant contact then theres not much you can do bet get a new one. Also taking it easy on them and keeping it dust free with a cover extends the life quite a bit.

The Bflat I mentioned had an odd response pattern. I played it for perhaps twelve times at medium velocity and then it would jump -not to full velocity but noticeably. I will be super careful when lifting up the strip and cleaning. I know some suppliers carry the strips and I've done work on them with the small three octave controllers. Thanks everyone for your input.