From VCFED:

An Olivetti M24 monitor can be opened and serviced. Make plenty of photos before that. The monitor must be discharged on the TV anode cap. I checked some videos on youtube on the subject. You need to disconnect first the input power and signal panel (where you plug the signal and power cable). Next you need to remove the circuit that goes on the back (attached to the TV yoke) by pulling it out (back). Next are all the cables plugged into the "motherboard". I had to mark them to know the direction and I used my photos. Remove a plastic rear holder that keeps the "motherboard" attached. In the end you need to slowly slide the "motherboard" back and up. One needs to be carefuller not to damage the bottom part where all the components and cables are soldered and pop put. The flyback transformer stays on the "motherboard" and it is extremely heavy and it could bend the entire board and damage it. I did not remove the TV anode cable/cap, but usually this is needed. I just did not want to break it. Make sure the monitor (or rather the TV) is discharged. The power supply can stay in.