Alas, I am having this problem with my old CS-2710 27" CRT TV when these problems that cropped up yesterday:
1) I have no video or audio in internal tuner mode.
2) When I switch my TV to line input mode I hear the audio from the VCR connected to the TV.
3) I can still hear the slight "buzz" through the TV's internal speakers when it's powered on.
Do I have a blown fuse, a blown component somewhere on the circuit board or a dead tube? 
I remember someone asking this same question on a slightly newer Mitsubishi 35" CRT and they said it could be a repair that costs over US$200 to fix if it's not a blown tube. If it's a blown tube I might as well get a new TV (which in my case will be a new VIZIO VO32L 32" flat panel 
).
