CRT whine - how to stop it?

November 18, 2004 3:53 PM

My CRT monitor puts out a high-pitched whine that changes tone depending on certain conditions of which I'm not familiar with (in other words, the tone fluctuates). It's not overly loud but it's definitely noticeable - it's quite irritating. It used to do this about a year ago then stopped only to start again last week. Anybody know why it's happening and how to stop it?
posted by ashbury to Computers & Internet (10 answers total)

The same thing happens with many TVs. It's just a sign that your CRT is wearing out. How old is it? This was one of the main reasons I switched to LCD when I got rid of my last monitor.
posted by Voivod at 4:02 PM on November 18, 2004

If the noise fluctuates above 16 KHz it might be a failing or poorly mounted flyback transformer (used to drive the retrace portion of the deflection yoke horizontal signal). The change in pitch can be from thermo-mechanical changes within the enclosure - say, a loose transformer gets looser as the cabinet heats up. Try whacking the cabinet :-) Sometimes a bad cable connection - even an exteranl one - can actually result in noise. Bit of a straw, but costs nothing to grasp at it. If you should decide the poke around inside the cabinet to look at things, be v-e-r-y careful - Very Large Voltages lurk in there and you can be badly hurt. Best left to a technician who knows what's touchable and what will knock you on your ass (and how to safely discharge those lurking voltages).

I lurve my LCD display and was happy to see my CRT go - although they still seem to rule for truly high-res work.
posted by cairnish at 4:23 PM on November 18, 2004

By the way - those voltages will still be there even when the thing is turned off. A CRT can serve as a Big Honking Capacitor. For heaven's sake don't ever poke around with the thing on.
posted by cairnish at 4:27 PM on November 18, 2004

Yeah, it's probably the flyback transformer. This is a pretty typical thing to happen to monitors when they start getting old, and unfortunately there isn't a good way to fix it. Here's a reasonably informative message with more details.

Personally, when my monitor did that, I used to just whack it on the side... often, the noise would go away for a while. That's not exactly a good long-term solution though. Also I found that it would shut up after the monitor had warmed up for an hour or so.
posted by xil at 4:28 PM on November 18, 2004

I've had that problem with my CRT before, but I've found it goes away if I turn it off and on a few times. The whacking method works too, but you're probably SOL if you're looking for a real fix.
posted by Orrorin at 5:26 PM on November 18, 2004

Are your speakers next to it? If so, consider moving them away a bit they could be causing some frequency problems. If not, sometimes that hum is indeed caused by some kind of unwanted AC noise... perhaps try plugging the monitor into a different outlet? There is also a possibility of some kind of electo-magnetic interference but, most monitors have an in-line magnetic sheild to help with this stuff. Just some thoughts... I agree with cairnish about the flyback mounting. Sometimes, just screwing them down a bit tighter helps.

By the way, does the monitor hum when it's not plugged into the PC?
posted by Dean_Paxton at 7:07 PM on November 18, 2004

Cheap monitors will also do this when they're placed next to one another.
posted by SpecialK at 7:15 PM on November 18, 2004

You may also find changing the refresh rate will affect the noise. If you're using Windoze, Right click on your desktop, select Desktop Properties, select Settings, Click on Advanced and then click on the monitor. Try a different megahertz, they may change the size of the screen or not work, but I've noticed if you have a very high refresh rate some monitors will have a very high pitched noise. Better than whacking your monitor.
posted by inthe80s at 8:17 PM on November 18, 2004

BTW, it probably is fluctuating according to the overall screen brightness.
posted by smackfu at 10:26 PM on November 18, 2004

inthe80s, you ROCK! New sign ups are sooo good. Everybody else, thank you for the advice. At least I got some aggression out on my monitor by beating the snot out of it. :)
posted by ashbury at 3:05 PM on November 19, 2004