[sdiy] Roland JX8P maintenance

[Florian Anwander]

Hello Stee

 > Most of the membrane buttons barely work.
These are not membran buttons, but real momentary switches under a 
membrane. Roland used ALPs KHC-10901, but other brands make identical 
buttons using other names.
Buy a bag of them, desolder the old ones, solder in the new ones.

Having an electrical desoldering gun will make your life much easier.



 > Several of the keyboard keys have issues. Mostly not generating a 
note, or too low "velocity". One key is somehow mechanically bad, 
resting slightly angled. (I
 >  have not opened the whole thing yet).
This is an issue of the keyboard switches. The JX-8P uses a quite 
oldfashioned key switching (the 3P ist more modern). The switches 
consist of copper blades:
http://pics.studiorepair.de/Roland/JX-8P/After_Touch/slides/Roland_JX-8P_9.jpg
If those corrode, then late contact (=bad velocity) or non working 
contact is the consequence. Cleaning those is not really easy. One can 
try chemical contact cleaners, but you have to be sure, that you spill 
out the contact clead well.

I tried the same with my Juno 6  (similar but not identical keyboard), 
and ended in cleaning the contacts with a fibre glass pencil - this is 
the job that Dante planned for his 10th ring of hell of his inferno.



The distortion is assumingly caused by the BBDs in the chorus. Does it 
disappear, when you switch off the chorus?

Florian