Monitor hisses with power off

First thing: check for a tire losing air. (sorry, couldn't resist)

You don't say if it is a CRT or not, but if it is, could this be the tube itself losing vacuum? Just a wild guess...

I swapped the ac filter and replaced a really burnt looking mosfet (630) but she still hisses--the hissing changes volume as you wiggle the ac filter (which is why i suspected it in the first place) maybe its one of those power regulator caps on either side or the coil immediately in behind...don't really know.

and yes its a crt and all inflatable objects have been moved from the room ;)\

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Are you serious?

SNAKE!!!

hissing

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No if the tube were losing vacuum enough to make a hiss it would cease functioning in a fraction of a second.

More likely the inductor or transformer in the monitor's power supply has a loose core.

but

A capacitor won't hiss. Sounds like something is resonating, replacing the filter is probably the easiest, or you could try to open it up and shoot some clear silicone caulk in there.

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If this was the case would the hissing stop as it is powered on? I'm by far no expert, just some guy trying to learn a thing or two..

far

Quite likely, when it's turned on the power consumption rises dramatically, does it have a standby mode when it's "off"?

Sounds like the AC input choke is singing just like the Mits use to do.

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Replaced the larger AC choke and it made no difference--still the hissing/squealing with power off. And yes it does go into a standby mode where it will show a "no input signal" that moves slowly around the screen. I noticed there is a smaller choke in there as well but i don't have a replacement handy for this so any other suggestions would be appreciated!

Thanks!