I have a ME-50 Electone Keyboard that suddenly stopped working. I need some guidance in trying to find the cause. I'm specifically looking for a service manual. I've contacted Yamaha and manual is no longer available. I've looked on line and found one a greedy seller is showing for $48 shipped, not in my budget this year. I'd be happy with a digital copy if someone could point the way. Or provide a tip as to what the failure is. Thanks.