Cary SLI-80 Tube Fuse?

My amp has 2 fuse holders for "Tube Fuse". They are rated .5A @ 250V. Is this a place where I could put one of those fancy fuses into, or is it just the fuse to the heater element in the tube? I wouldn't want to spend the $$ on a fuse to the heater element. Also the manual says there is an AC Fuse on the unit as well (3A Slow Blow 250V). Does anyone know where this is? I hope it's not inside the "bird nest", that is under the bottom plate.
I've once owned that amp (great btw). The a/c fuse is adjacent to the power cord IEC. As I remember, it's a small plastic door/cover that pops open w/a small screwdriver & the fuse is held in place horizontally & I believe there is storage for a spare under the door/cover. I once had to change that fuse when a 5U4G rectifier shorted & blew & took out the fuse. IMO, I wouldn't mess w/so-called fancy fuses. The manufacturer of my present amp is strongly against the use of them in his amps as they have caused alot of problems.