Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!cornell!uw-beaver!tektronix!orca!tekecs!titus!morganh
From: morganh@titus.gwd.tek.com (morganh)
Newsgroups: sci.electronics
Subject: Re: need help to reduce a monitor's squeal
Message-ID: <10409@tekecs.TEK.COM>
Date: 28 Sep 88 15:43:52 GMT
References: <716@pedsga.UUCP>
Sender: nobody@tekecs.TEK.COM
Reply-To: morganh@titus.UUCP ()
Organization: Tektronix, Inc., Wilsonville, OR
Lines: 31

In article <716@pedsga.UUCP> jeffj@pedsga.UUCP writes:
>I have a question worthy of the net's collective wisdom.
>My hearing extends into the high frequency end (>15kHz).
>
>I can hear several terminals and televisions 'squeal'.
>I understand that this is the flyback transformer at the scan frequency.
>
>Is there anything I can do to attentuate the squeal?
>...

:-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-)

Have I got a solution for you!  It includes (1) John Deere model MC Crawler
Tractor sans muffler (the old two-cylinder "poppin johnny"), several older
chainsaws in which the exhaust baffles have been eaten through, and .44 magum
and .375 magnum handguns.  Mix well with a lack of ear protection and sheer
stupidity over a number of years.

I am a glowing example of the efficacy of this treatment.  I haven't been
bothered by outside high frequency sounds in years.  My ears begin rolling off
at about 4500 Hz (of course the tinnitus keeps my desire for high frequency
sound satisfied with CONTINOUS mixed squeals..)
:-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-)

Seriously, however, when I could hear such things (working on old TV sets), it
was almost always connected to some sort of corona discharge around the
flyback.  You might check with a local supplier for what we used to call
"Corona Dope" -- it used to solve the problem for me.  To diagnose, try
operating the monitor in a pitch black room with the back off.

Morgan