"Nutcase Kook"

Arcing/sparking wiring/mains-outlet at a venue. Lead to vaporised and neat
silvery metal condensed ring and then black deposit in 4A(T) internal
mains fuse, presumably something like 50A to do that.

** No problem for a large toroidal to draw 50A surge current.

That Yamaha has a 400 or 500 VA job inside and no soft start system.

Measure the primary ohms and divide that number into 240 - gives you a
close approximation to the max possible surge current at switch on.

With an intermittent AC supply connection, max sized surges are guaranteed.

Just replace the fuse - add a 5ohm NTC if you like.


..... Phil