iMac Bondi Blue 1998 won't turn on

[viksn0w]

Ok yesterday worked fine, but now I wanted to set it up for an old fashioned Internet Browsing and I pressed the power button and nothing. The iMac seems almost dead, but there is still the "bzz" noise that comes from it, I think from the cathode-ray tube, this noise it's really low but It can be heard and this noise usually comes when the iMac is connected to power.

Someone knows how to fix it?

[viksn0w]

Now I found out that when I click the power button, this sound changes to a lower frequency

[Astroman]

you probably refer to the standby sound this kind of Mac emits, very low level but annoying by it's high frequency.
I remember pulling the plug from the wall outlet back in the days to avoid it...
The tube is unlikely to fail (if you didn't observe changes in video/color quality), but the power supply is the usual suspect.