Another DIY synth repair Q, rubber membrane switches failing

[Reezekeys]

Several switches on one of my Roland A800 Pro's front panel are acting up. Three of them take a lot of force to actuate, and one doesn't work at all. Knowing how these switches work I assumed dirt got underneath the bubbles so I disassembled and swabbed the circuit board with IPA but that didn't fix it. My next assumption is that the carbon dots in the bubbles are worn. Years ago I remember seeing someone using a peel-off strip of small carbon dots to renew these kinds of switches but can't seem to find that or anything similar now. Is there any kind of hack or trick I don't know to getting that small dot to be conductive again? I'd consider buying the entire assembly but Roland doesn't sell parts to end users anymore and Syntaur doesn't have these at the moment either. I'm on the lookout for a used A300 Pro to cannibalize from, but used prices on those are pretty high right now. TIA for any tips!

 

 

[Coker]

Try Syntaur

[Reezekeys]

Thanks but I mentioned in my post that Syntaur doesn't have this part.

[Old No7]

I searched on "carbon dots" but the links referred to something more scientific that I am!

 

That said -- check Amazon and search on "tactile push button switch micro" and you may find something similar.

 

Old No7

[Reezekeys]

Thanks. I've searched on "bubble switch" and "membrane switch" among a few other terms. Just tried "tactile push button switch micro" and get lots of these - not what I'm looking for unfortunately!

 

And yes, "carbon dots" returns a lot of things not remotely connected to any kind of switch!

 

[RichieP_MechE]

I associate these types of rubber buttons with TV remotes. Searching for "remote control carbon button" turned up a few things.

https://www.ebay.com/itm/264383555845

https://www.amazon.com/CaiKot-Conductive-Silver-Coating-surfaces/dp/B003D8G8SY
https://www.sciplus.com/keypad-fix-45985-p
https://www.ebay.com/itm/134102575450?chn=ps&var=433547190186

[Reezekeys]

Thank you! This looks exactly like what I need. I needed the correct search term and you had it!

[aronnelson]

There is a "kit" to repair these buttons. I bought it but unfortunately never had to the time to test it. Was going to try it on an old JX-3p. Apparently it is supposed to work.

This is not the one I got, but you get the idea.

 

TV Remote repair kit.

 

 

[Reezekeys]

Thanks, but I already pulled the trigger on this:

 

 

I will report on how well it does the job! It's a different way of attacking this issue than the others, which seek to recondition or repair the actual carbon in the switch - this product replaces it completely.

 

BTW the product you linked to was also mentioned in Richie's post above, at a better price - https://www.sciplus.com/keypad-fix-45985-p

[Reezekeys]

I'm back to say this "Button Worx" repair kit did a great job for restoring normal function of the few buttons on my A800 Pro that were requiring me to press very hard to actuate. I still have one button that doesn't work, but I'm pretty sure that's not a contact issue. I'll be bothering the electronics experts here very soon with a new thread regarding that one button! 🙂 

 

These are "peel & stick" conductive carbon switches that replace the carbon dot or pad in membrane switches (they're applied to the circuit board and you don't need to do anything with the existing carbon pad). They're made more for TV remotes so have a variety of shapes & sizes, which is a bit of a bummer as I'm gonna be left with a lot of unused ones - I only needed the top eight 5mm dots. I can't complain much, $11 has to be a lot less that what Roland would charge me for a new board assembly - if they would sell me one, which they wont!

 

 

This is the membrane switch assembly with the carbon pads -

 

 

Here's a pic of the board with my dots applied to the first three and last switch:

 

 

And a close-up. I needed to trim a bit to accomodate the tiny LEDs in the middle. The A800's switches illuminate when pressed:

 

 

I'm not sure if this product would work for bubble switches on a keyboard, due to how velocity is calculated. Since these dots add a small amount of height to the circuit board, they may cause notes to actuate earlier, or have different velocity response than notes without the dots. That's just my guess. I'll add that cutting, trimming, peeling the adhesive backing and carefully placing these guys can be somewhat time-consuming if you have a lot of them to do. I would probably go with the "paint-on" conductive products for a keyboard.

 

My switch #9 does not work, but as I said I'm pretty sure it has nothing to do with the issue I was addressing with this product. The first three buttons now work like new, actuating with a very light press. I would recommend this product for anyone having similar issues where cleaning with IPA didn't solve contact issues.

 

[EDIT - button #9 is fine! I got bit - AGAIN - by the weird Roland "feature" of a system setting that lets you assign this button to HOLD (CC #64) instead of what you program it for! I swear this setting changed on its own! This happened a few years ago too. Look Roland, if my sustain pedal fails or I forget to bring it, I can easily assign any button or pad to send sustain. Why this has to be an obscure parameter setting buried a few layers into a system menu is beyond me. Not to mention one that apparently can decide to activate on its own!]