Technics piano SX-PX665 burnout
 

Our Technics SX-PX665 piano has suffered a catastrophic burnout of the
output stages - power amps, loudspeakers, and headphone o/p all
destroyed themselves - nasty burning smell, and lots of horrible
buzzing until it all went dead. We got it fixed (power amp mended, and
the speakers replaced) and it all worked for about a week until the
same thing happened again. How can we prevent this from happening?
Anyone got a fix?