Welcome to NLG, I see this is your first posting here.
Sometimes a buzzing sound on a crt type monitor is the high voltage/flyback transformer arcing. If you can safely get into position to look at the monitor circuit board while it is buzzing with the room lights dimmed you might be able to see blue arcing on the outside of the flyback or on the crt glass where the heavy anode lead attaches. Another thing that can buzz is a relay on the monitor board that is quickly turning on and off. Do you mean you removed the monitor and powered up the machine, no buzzing was heard, indicating the sound is coming from the monitor? What size was the fuse your replaced?
Is this a new machine to you, or was it working for some time and then this happened? Post photos of the machine and the monitor so they can be identified, including any nameplate on the monitor, that will help with the questions.