I have an NEC XM29 Plus monitor which works great however when on an input that uses 15khz it starts to make this really irritating high pitched noise once it gets warmed up. I realize all crt's have an inherent noise but this is much more audible than that. It can be heard in other rooms in the house and is starting to get on my girlfriend's nerves. After doing some research I saw a couple threads pointing out the flyback transformer as the culprit. Does anyone here know what about the flyback is causing this? Is there something I can do to it to get rid of the noise or does it have to be replaced? I've never worked on a CRT but am pretty handy with electronics. How dangerous is it to work on this specific component inside the monitor? Any help is appreciated.
The flyback transformer, or LOPT, is the most dangerous component in the monitor, bar the CRT, perhaps. It operates at tens of thousands of volts (probably 20-40kV). Yes, it would need replacing. I would STRONGLY advise not doing it yourself if you are not familiar with television repair. Take it to a television repairman.
For anyone possibly coming to this thread in the future - I looked around for a tv repair place and wasn't quite confident in taking it to places that seem to deal with mostly HDTVs these days. I cracked open the tv. There are about 8 big screws (2 on the bottom of the tv so it has to be put glass side down) and 6 little screws around where the inputs are. The three big screws closest to the glass should not be taken out. I had to yank pretty firmly to get the back case off the first time. After cleaning out the cobwebs I eventually pinpointed the noise to a smaller secondary flyback transformer. Apparently this tv has one huge one at the bottom and another small one on the board on the left side of the tv (when facing the screen). I could poke the capacitor on the underside of the exposed board and get the squealing to get really loud or to stop. I didn't have any toothpicks but I took a plastic fork and broke off one of the points and jammed it in horizontally under the arm that goes into the transformer and put hot glue over the top of the arm covering the fork piece as well. So far the noise has not come back. It can be tough to pin point the source of the sound at first but I had a db audio meter I used to pinpoint the noise. You could use a paper towel cardboard tube or something to pinpoint the sound. On a separate point I wish I could shut those fans off or slow them down as they are a bit of overkill for home use. You can't disconnect them though as the tv shuts off after 5 seconds if the fans aren't plugged in and working. A guy did a mod on his NEC on the shmups forum but it was a bit over my head.
lol @ the ghetto repair, i like it, not sure how well it'll hold out though lol. fans could maybe be replaced with more quiet modern fans such as pc cooling fans? i'm not familiar with this tv / monitor so cant really help much in that regard. but if the fans run of 12v or even 5v then they should be easy enough to replace
Id be interested in that. My Mitsubishi XC3730C annoys the shit out of me with the loud volume of the fans.
I'm not sure about the Mitsubishi but I've heard the NEC doesn't work with any other fan than what it came with. Theres some sort of voltage check going on there and if 10v isn't there then it shuts off. It'd be nice to swap out with some quieter fans as thats a really easy fix.
