Casio CZ/ VZ/ FZ - Pro Series

Weird. After opening it, it's working a bit better. Just opening it. I 
noticed that when the sound is gone, if I move the keyboard (it's now 
unscrewed) the sound returns. In fact, if I press the keys gently the 
sound works, but if I press harder sometimes the sound disappears again 
for some seconds. Plus, one of the rectifier diodes look a bit burned, 
in the small circuit board at the bottom right. My sixth sense is 
telling me that it's going to be easy to fix the problem, but what's 
confusing me is the fact that moving the keyboard fixes for some seconds 
the sound. All the cables are firmly attached to the circuit boards, so 
I'm not sure about what to think. Maybe the vibrations make the 
rectifier diode make better or worse contact with the circuit board? 
This component looks a bit burned, but it's firmly soldered to the 
board. Any ideas? Thanks again, at least I'm pretty sure now that the 
synth is still alive and it's going to survive :)

Manu