Screen is black, No Input Signal

try changing input or source if same bad power board

Well one time I had this problem with my Nintendo 64 console when I was in the middle of playing perfect dark the screen had froze went black and then it went to saying no signal on the tv screen. The console did not over heat to cause this problem. I thought that it had died on me but I had tried a new expansion pack and it was fine after that. SOmetimes the expansion packs can blank out in the middle of a game play they can die without a warning then. Or it can say expansion pack needed or it will give the white flash that it is turning on but nothing happens after that then.

My first thought would be to check your TV on multiple inputs to verify that it IS the TV and NOT isolated to your input cable(s). If you can get a solid blue color to come up on the screen by changing inputs then it would really narrow down the issue(s).
Hope this helps.

Only the older Analog type televisions get snow from lack of signal. The modern Digital TV gets pixilated. like missing pieces.
And on re-reading the title of your question, it does say CRT...... As in Cathode Ray Tube. (I thought they were all gone now, all around the world) Anyhow.... has your country switched off it's analog tv transmissions. This would give you snow. Because there is no Transmission. Seems unlikely they would stop transmission in the middle of what your watching.
So
Do you have a Digital Set Top Box feeding the TV? This would pick up Digital TV transmissions and convert them to your old CRT TV Screen. Knowing this should help you diagnose the problem.
Check the antenna input to your digital box and connections from the STB to your TV. They probably use a Yellow video cable and a Red & White (Sound Left & Right). You didn't mention if sound was still there?
Perhaps someone has pressed the remote control and the TV has jumped to one of the Antenna Channel inputs rather than the Video input (Yellow Video input)?
Might be that Simple.....
Good Luck

try to change another input device...

sounds like the video card went out or the cable shorted can you try that monitor on a friends computer?

see if u have an input button on remote,if so keep clicking it

you possibly have a bad video wire. try a new pair and see if it still does it. if probly still exists you may have a short in the bose or even you signal source