Dead keys on your Roland JX3P??? Chances are you can fix them for free, and all you need is a Cornflakes box.

First, open up your JX3P by removing the screws via the access holes in the plastic side-panels. This will allow the entire control panel to tip backwards on it's hinges. Next, remove the plastic key in question (it's pretty easy, they're just latched in). Underneath the key you'll see a rubber circle, which is the key contact. Power on your JX and press this with your finger (don’t touch anything else - you might die). There’s a very good chance that this contact will produce sound. If it doesn’t, then apologies, but you have to go visit a real repair centre. 

But if it does make sound, cut a thin strip of cardboard (Cornflakes box) about 1.5 cm’s long, and the same width as the bottom of the key. Sellotape this strip to the bottom of the key, lining it up above the rubber contact. You should find that the reassembled key once again triggers perfectly due to the extra pressure being exerted. If you like, you can go on to superglue the strip in place for a more permanent fixture, and perhaps consider using thin plastic sheeting instead of cardboard. The choice is yours.

I’ve had four keys running this way for over two years now, and I learnt the trick the hard way: Dropping my JX3P into an Authorised Roland Repair Centre and getting charged for it…..
(and check the link below for spare parts )