Re: Apple RGB Monitor Making Very High Pitched Noise

[dmcclain@runet.edu (Dennis McClain-Furmanski)]

Tom Kelly (tomk@pro-nsdapple.cts.com) wrote:
: In <Pine.ULT.3.91.951207112942.14160B-100000@cda.mrs.umn.edu>
: "Adam Gurno -- \"Certified Geek\"" <gurnoab@cda.mrs.umn.edu> writes:
: 
: >I meant to say, at the end of my last post, to turn them all OFF and then 
: >bring in the student to find the one that's on. (there are none).  That's 
: >what you get for posting late.
: >
: 
: You make it sound like it is NOT really a problem in your post.
: I can hear monitors and TV sets when they are on.
: I am 41 years old.  True I do not notice it like I did when I was a child, but
: I still can hear it.  I never found it to be a problem (for me).
: It could be a problem for some people.
: IT IS A REAL SOUND!!!

It is a real sound. It comes from the transformer's chattering with the 
collapse of the field it generates while pushing the vertical scan and 
vertical blanking. The frequency is 30 x 525 or 15.75 KHz. I literally 
grew up in a TV store. I could hear it all the time. My dad couldn't 
anymore due to aging, but used to be able to and knew what it was. I sold 
at least a couple TV's based on them producing the least amount of this 
sound. People who were sensitive to it would come in and ask, and since I 
could hear it, we'd go around turing them on one by one until we found 
one that was relatively quiet.

Here's a sometimes fix:

Loosen the transformer from the board and place rubber grommets between 
it and the mamaboard. This cushoin sometimes keep the board from acting 
as a sounding board, amplifying the problem. If that doesn't work, the 
only other fix that has ever worked for me is changing the transformer, 
and that's not a reasonable fix for even the techishly oriented. 
Transformers aren't cheap.