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From: bart@reed.UUCP (Bart Massey)
Newsgroups: net.audio,net.micro.mac
Subject: Re: Re: "Ultrasonic" hearing
Message-ID: <2333@reed.UUCP>
Date: Fri, 17-Jan-86 16:47:19 EST
Article-I.D.: reed.2333
Posted: Fri Jan 17 16:47:19 1986
Date-Received: Mon, 20-Jan-86 04:02:15 EST
References: <1280@brl-tgr.ARPA> <590@harvard.UUCP> <11370@ucbvax.BERKELEY.EDU> <251@birtch.UUCP> <1115@oddjob.UUCP>
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Organization: Reed College, Portland, Oregon
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Xref: watmath net.audio:7210 net.micro.mac:4150

> (To net.micro.mac readers:  this has been an ongoing discussion in net.audio,
>  but as this posting is a bit of a digression from audio talk, I have directed
>  followups to n.s.m.)
> 
> In article <251@birtch.UUCP> oleg@birtch.UUCP (Oleg Kiselev) writes:
> >>     I've never encountered a TV receiver or monitor that
> >>didn't emit an annoying high pitched squeal at at least a
> >>low audible level.
> >
> >I have heard it is usually the vibration of transformers and/or capacitors
> >(fly-back transformer?????). THe worst offenders I have heard were 
> >tvi925 . Sometimes a sharp rasp on the side of the terminal would silence
> >it for an hour or so ( and many people got so irritated by the squeal they
> >did it routinely).
> 
> I have had the same problem with my Mac, and also found that the "sharp rasp"
> (read: "swift kick") solution is usually effective.  Why is this?  I never
> had the problem before I blew my power supply, and had to replace the analog
> board.  Can anybody suggest a possible solution (or a reason why this problem
> would suddenly crop up, for that matter)?
> 

	My old high school electronics teacher said that it is in fact the
flyback transformer vibrating (which makes sense) after it has worked a little
loose from its mounting bracket.  He claims he'd fixed many of them by shimming
them with pieces of toothpick.  WARNING:  THIS IS A HIGH VOLTAGE AREA!! DO NOT
TRY THIS UNLESS YOU KNOW EXACTLY WHAT YOU ARE DOING!!! I WILL NOT BE
RESPONSIBLE FOR YOUR ELECTROCUTION!!

					Bart Massey
					..tektronix!reed!bart