Newbie: Help needed for replacement piezo roland octapad II

Hello all,

So I am kind of a newbie to DIY, I only completed a Shruthi kit and some basic repair of some racks at home as well as soldering my own cables…
I just received a Roland Octapad II. It is a nice and solid gear but it seems that some pad (more than half of them) are not sensitive anymore, I really have to hit like a crazy moron on some of these to get a velocity response.

I opened the beast and noticed that most of the piezo have white oxidation/ things around the soldered cables on it, I am not sure if it really is a problem but well…
I plan to change the piezo captors, they are easily accesible.

As I am a newbie to DIY and electronics, I am not sure what kind of piezo I have to source, I measured them, they are 35mm piezo.
But is there a specific voltage, frequency needed? I found these at http://www.gotronic.fr/art-disque-piezoelectrique-dp035-3843.htm

I’m not sure which kind of piezo I should take and where to find them.

So i would be really glad to read any input for the changing of these piezo and any help about how I should proceed in order not to destroy the whole thing (it still costed me a decent amount of money).

Thanks a lot in advance and sorry for being kind of clueless, i’d rather be careful and ask infos where there are serious people (this forum).

I think you could use about any piezo in there… just be careful and work slowly. I don’t know if your piezo’s are the real problem but if it’s easy accessible it can’t hurt to try and replace one.

Hi shiftr,

Thanks for your answer,
If I can use any piezo, that is great news.

Well, I think that it comes from unsensitive piezo, because 2 pads on the 8 are completely fine. I do not know if it is a coincidence or not, but these two functional pads are located under the main circuit board, kind of protected. Could it be that they were kind of protected from whatever happened?
the guy that sold it to me swore it was 100% functional last time he played, which means like 10 years ago (no he did not find useful to test it just before sending it to me…).

So I am just assuming that the piezo aged badly, sitting somewhere in a corner…

You could try swapping them… ?

Also, have you tried rinsing them with IPA? Don’t think that there is any known reaction between piezo’s and IPA, although it may dissolve the glue…

V’ cent, what do you mean by swapping? Un-glueing and un-soldering the one that works fine on the ones that doesn’t?
IPA, is that the contact cleaning product?

That could be the first step…

IsoPropyl Alcohol. Better not get it Mixed up with the India Pale Ale type of beer which is near and dear, but of no use for cleaning stuff.

Make sure it ins’t a hidden velocity sensitivity setting first. Several synthesizers and samplers have different velocity curves, and one of them is usually all the way on when triggered and all the way off when not. Read the manual before doing any repairs.

@Jojjelito: IPA makes a great pallet cleanser at fancy dinner parties.

Yup, I meant removing one that works, and testing it in place of one that doesn’t work.
IPA is isopropyl alcohol, it can be used to (attempt) clean off corrosion, it might work, it might not.
It will probably dissolve the glue, if you put too much IPA on it. Consider using a Q-tip, or something like that, no guarantee that it will work, but it might :slight_smile:

Thanks for all your answers,

I have a can of contact cleaner spray, I think it is what you guys are talking about (altough it is not written what’s in it).
I checked many times the different presets and also reseted the device to the factory preset, nothing seems to work…
I’ll try to apply some of this spray tonight and keep you posted.

I just used Q-tips and this contact spray I had.
No improvements, it juste removed a layer of some black powder that was on top of the piezo.
it is on every piez, even the one that are working fine, so I guess it is not an issue although this strange layer gets off when you touch it…

Hi guys,

I will go to the electronic shop of my neighborhood trying to see if they have piezo this size.
Do you have any input about how I should fix the piezo to the surface? What’s the best? Double sided tape or hot glue, epoxy?

Thanks again

Double side tape or hot glue is fine, epoxy is not a good idea, unless you don’t expect to disassemble it ever again.

Double sided tape is probably the easiest solution, since it has a even thickness…

Thanks man,

The guy at the shop only had 27mm piezos, I took one to do a test, but anyone know the actual difference between 35mm and 27mm? Is it only about the hitting surface?

Without a datasheet - no.

Alright, thanks a lot,
I tried anyway, and it worked like a charm!
I was kind of anxious about this but it actually works quite well, even with a 27mm piezo.
I still think I am going to order a dozen of 35mm, regarding the surface, it makes sense to stick with the original size.

Thanks a lot again everybody!

They’re certainly not that expensive … So good idea - I’m glad that it worked out for you, have fun :slight_smile: