Hissing, static from monitor?

My computer monitor is making an odd hissing, static-type noise. It’s coming from the monitor itself, as there are no speakers built-in. I can hear clearly that it’s coming from inside the monitor when I put my ear to the vents in the back.

It’s an HP 2509m and the display seems fine. The noise just started today.

Any ideas what this is? Is my monitor going to blow up or catch fire? Or just go kaput on me?

It will probaby go kaput on you, and soon. The power supply is likely going out - either a transformer or a capacitor is failing.

Much more likely that a capacitor is failing because transformers simply don’t fail in my experience, especially in modern switch mode power supplies (the noise occurs because the control loop becomes unstable as the capacitor loses its effectiveness, resulting in oscillations at a lower frequency).

It is possible to replace the capacitor (which may be easy to spot since they often swell up and split open) and repair the monitor, especially if it still works; complete failure can lead to damage to other parts. Note that if you do replace it, don’t use one from your local RadioShack or the like (e.g. general purpose, 85C temperature rating), it should be specified as low impedance and 105C (I have seen many manufacturers use the cheaper ones anyway, even once in a CFL where they get very hot).

Thanks. I unplugged it while I left the house for a while (safety first!) and when plugged it back in the screen was all screwy. Flickering fast and dim.
It’s a nice, big monitor so is it worth having it fixed? Or am I just in the market for another monitor?

Replacing any leaky capacitors should be trivially easy for anyone who does this kind of stuff. You may be able to Google the model number and “leaky capacitor” and find the exact location. My brother did this with some monitors he repaired. In fact I’m using one of the repaired ones at home.

Where the heck does one get a monitor fixed? I’ve checked with the local Staples that has a big “We fix computers!” sign out front and they looked at me like I’d dragged in a '54 Ford and asked them to change the transmission. They don’t do monitors, they explained.
I’ve Googled for fixing monitors and I get tons of shady looking, barely on-topic results. I called a couple and they both seemed to be an elderly guy in his garage who wasn’t eager to work on an HP product because “the parts aren’t available” or didn’t think he could fix it because “those big LCD monitors, boy, I don’t know about those things.”