All about the Roland Jupiter-series

Hi.

I've got a problem with my 6. It only happens sometimes, and seems to 
only happen when it's hot, or when it's been on for a while. 

One of the voices drops in and out, creating large "popping" noises. 
This is always either voice 2, 4, or 3 - and often they drop out in 
that order.

I've tried disconnecting and reconnecting all the connectors, but it 
doesn't seem to have done the trick?

Any ideas?
Thanks, James