Yamaha MOXF8 keyboard, one note plays too loud!

[David Farber]

This Yamaha MOXF8 keyboard has one note that plays too loud when more than
the slightest of pushes is given. I moved the keypad underneath to a
diffenerent octave and the problem followed the keypad. In other words, the
note that was too loud, switched to the same note but in a different octave.
I can't see anything visually wrong with the keypad contacts. There are two
pc contacts per note. One rubber keypad contact opposite the pc contact
extends just a hair more than its adjacent rubber keypad contact. How does
this translate into detecting how loud to play a note and how do you think
this relates to the note that is too loud?

Thanks for your reply.
--
David Farber
Los Osos, CA

[Pat]

Total guess on my part, but it probably detects how fast you press the
key (rather than how hard you press). If the two contacts are made
simultaniously, it thinks you want a loud note. (Or maybe, one
contact is stuck on? Or, an input port on an I/O chip is bad?) Good
luck.

[N_Cook]

Usually 2-stage contacts, and timing the difference.
Can you swap a pair of the silicone contact pad strips over , to another
part of the keyboard to see if the problem moves with it.
Check pull-up/down Rs between adjascent keys?
Can you easily swap a multiplex line over with another?

[Jocelyn Goodey]

Try wiping the carbonised contact pads with an cotton bud soaked in IPA.
If that fails try a gentle rub of the black pips with a fine emery board &
wipe with IPA again.


Regards Joss

Tetigisti acu (Titus Maccius Plautus 254-184BC)

[Clifford Heath]

It's a dual-contact pad. One of each pair should contact before the other.

This behaviour is what happens when the early contact fails, and the
late one does not. The controller sees nothing, followed by the late
contact, so it assumes a high-velocity key-stroke and plays full volume.

Fix or replace the early contact.

[David Farber]

Hi Clifford,

I will replace the pad assembly. Thanks for the great explanation.

[N_Cook]

Isn't that interpretted as a non-key press, a dead note, second contact
only. I seem to remember simulating that, with placing a piece of paper
under the first contact.

[Clifford Heath]

You might have had them switched around.

It's not possible to trigger on the first contact,
because you don't yet know how fast the key-press is.
So instead you trigger on 2nd contact - if that never
happens there should be no trigger.

Clifford Heath.