How do I change a Blown 312 4a 250v fuse

The power supply has failed. Replace the board.

They have a restorside, a bit , that's why you have fast and slow fuses. But if they were dead, then the resistant would be infinite, so
no problems with both fuses.

gr. Richard

Fuses are either blown or not. The hum is from an ungrounded or unshielded cable somewhere.

What required the fuse to be changed in the first place?

Unplug the fan.
Open it up carefully.
Look at the the wiring for damage or shorts.
Check that the fan impeller is free to turn.
If all of the above is OK then possibly the motor has gone? If so then it will probably be cheeper to buy a new one.

My BBL600XL stopped working because of a blown fuse. You need to remove the phillips and torx head screws out of the bottom. Then remove the base. There you will clearly see a fuse on the circuit board.

It appears to be a 10A 250V fuse.

http://www.newark.com/littelfuse/0215008-mxp/cartridge-fuse/dp/42K9308

Fuse is a "Littelfuse 0215008.MXP"
8A 250V Slow-blow ceramic

Buy at Radio Shack. 1.99
1.5A 250V 3.6x10mm Fast-Acting Ceramic Fuse

I can't believe he pulled them all, but here's a list of all the fuses and their ratings from the service manual:

S 1000 Fuse, T 5A IEC
S 1300 Fuse/Clip, 5 Amp, 250V
S 1801 Fuse, 2 A, 250V IEC
S 1804 Fuse, LT 1A, 250V, IEC
S 1805 Fuse, LT 1A, 250V, IEC
S 1700 Fuse, 2 A, 250V IEC
S 1701 Fuse, 2 A, 250V IEC
1003 Fuse, 500MA, 50V, UL

The fuse which you have used is of correct rating 250v/5A, the switching regulator of the SMPS primary section is faulty, so the fuse blows of continously