Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!sjsca4!greg
From: greg@sj.ate.slb.com (Greg Wageman)
Newsgroups: comp.sys.atari.st
Subject: Re: Noisy 1040st??!!
Message-ID: <1989Nov27.223937.19134@sj.ate.slb.com>
Date: 27 Nov 89 22:39:37 GMT
References: <1989Nov23.031757.9434@aucs.uucp>
Reply-To: greg@sj.ate.slb.com (Greg Wageman)
Organization: Schlumberger ATE, San Jose, CA 95110
Lines: 25

Opinions expressed are the responsibility of the author.

In article <1989Nov23.031757.9434@aucs.uucp> 880139h@aucs.UUCP (Rob Hutten) writes:
>
>    My 1040st buzzes.   It's not the monitor, it definitly comes from the
>machine itself.  It's a real highpitched whiney buzz that seems to come
>from somewhere on the left side.  What's more, the pitch of the buzz varies
>with whatever is going on on the screen, e.g. a higher pitch with a white 
>background and lower pitch with a black background. 

The Atari ST's use a switching power supply.  Such power supplies
contain toroidal (donut-shaped) transformers wound on ceramic cores.
Sometimes the windings are loose enough that the high-frequency
switched magnetic fields causes them to vibrate on the cores,
producing the sounds you hear.  You or your dealer could apply a
material called "corona dope" (usually used on television flyback
transformers) onto the toroids to stop the vibration.

This is a very common phenomenon with switching supplies.


Copyright 1989 Greg Wageman	DOMAIN: greg@sj.ate.slb.com
Schlumberger Technologies	UUCP:   {uunet,decwrl,amdahl}!sjsca4!greg
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