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From: david@wiley.UUCP (David Hull)
Newsgroups: comp.sys.mac
Subject: Re: a different kind of SE screen quirk
Message-ID: <1506@wiley.UUCP>
Date: Tue, 20-Oct-87 19:10:50 EDT
Article-I.D.: wiley.1506
Posted: Tue Oct 20 19:10:50 1987
Date-Received: Fri, 23-Oct-87 02:10:09 EDT
References: <1660@mit-amt.MEDIA.MIT.EDU> <458@sdacs.ucsd.EDU>
Reply-To: david@wiley.UUCP (David Hull)
Distribution: na
Organization: TRW Inc., Redondo Beach, CA
Lines: 38
Keywords: screech, hum
Summary: Power supply makes noise

In article <1660@mit-amt.MEDIA.MIT.EDU>, (Adam B Rosen) writes:
> When scrolling through
> a large document, say in Word (any version) or downloading text via modem,
> as the print scrolls up the screen the Mac makes a very faint 'pulsing'
> noise with each line....

In article <458@sdacs.ucsd.EDU> wade@sdacs.ucsd.EDU (Wade Blomgren) writes:
> An acquaintance of 
> mine, upon hearing the description of this problem, surmised that it could 
> actually be the 68000 processor (or the ROM?) doing the screaming, as the 
> tightly looped set of ScrollRect calls is executed. He had seen a similar 
> thing in a lab full of AT&T boxes. (Meaning that there was some fairly common 
> activity that started those processors humming).

Well, my Mac SE does this too.  I just noticed it about a month ago
(I've had the SE for about six months now), so I don't know if the noise
started just recently or if it has been there all along.

I'm pretty sure that it's the power supply making the noise.  We had a
couple of Sun 2s at work that had the same kind of problem--executing a
program would cause it to make a loud buzzing noise.  Replacing the
power supply cured the problem.  I think that as the CRT and the 68000
draw current during a scroll it causes the power supply to make noise.

> Regardless of the cause of this particular glitch (avoidable or not),
> I am not impressed with the QC on the Macintosh SE.

I agree.  I've had mouse clicking problems, disk ejection problems,
the loud fan, and now this.  My screen doesn't normally wiggle, but I
can make it do so if I hold my hand over the fan outlet on the back.
Anyway, the noise isn't a catastrophic problem.  As you say, the fan
practically drowns it out.  But annoying, all the same.

-David
-- 
					---------------------------------------
					David Hull  TRW Inc.  Redondo Beach, CA
					  ...!{uunet,cit-vax,trwrb}!wiley!david