This odd hissing noise: did it occur during the repair, or after you tried to turn it on? And was it fairly short-lived, or did it exist until the machine was turned off?
If it was short-lived and happened with the case off while you were fixing something, it's probably a broken CRT.

However, if it only occurs when it's turned on and disappears when turned off, it may be a bad component on the analog board.

Some more data would be useful.

Click to expand...

yes, I concur...but it does sound like the neck was cracked, if so,

then the CRT is toast....they are very fragile around that area.

a few yrs ago, I was working on a friend's SE, and accidently bumped

that neck, and heard the HISS of death......

lucky, I had a couple of very nice, and virtually new CRTS...and

quickly changed it out...turned out it was a gooood thing for my

pal, as his 'original' CRT, suffered from burn in..from MS word..

weird seeing those ghostly images burned into the tube....

for a few yrs, after dark sold a boat load of those programs, i.e. flying toasters, fish, etc....