Thing is, the computer went through some rough shipping (the plastics from the reset and debugger switches was coming off and when i opened the case, I saw that the video board fell off and two pins were bent on the CRT) so I bent the pins back into place, reattached the video board, and powered it up. I then heard the hiss and yanked out the power cord in panic. The noise disappeared immediately.

PS: The first time I started it up, after I got it, there was nothing on the screen, signaling something wrong in the CRT/analog board area but I did get a normal startup beep and I heard the fans, meaning the logic board and the analog board (or at least the parts that power the logic board) are OK.

BTW: how can I tell if the CRT was cracked?