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From: chuq@plaid.UUCP
Newsgroups: comp.sys.mac
Subject: Re: Is my mac about to fry?
Message-ID: <21199@sun.uucp>
Date: Tue, 16-Jun-87 12:46:00 EDT
Article-I.D.: sun.21199
Posted: Tue Jun 16 12:46:00 1987
Date-Received: Thu, 18-Jun-87 04:08:31 EDT
References: <403@oswego.UUCP>
Sender: news@sun.uucp
Reply-To: chuq@sun.UUCP (Chuq Von Rospach)
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Organization: Fictional Reality, uLtd
Lines: 46

>I use a Mac 512Ke with Apple HD20 at home and with the recent warm weather
>it has developed a high-frequency (15-20 khz) "whine" after it has been
>on for awhile.  It only seems to happen on warm (over 75 degree) days
>after the computer has heated up.
>
>I've read a lot about power supply failures and I'm wondering if this is
>a prelude to a breakdown (I remember having a b/w tv years ago that did
>this for awhile before the flyback transformer went up in smoke...).

Actually, the power supply rarely fails (for details, read MacTutor).  But
it sounds like your flyback is getting marginal (the flyback happens to be
attached to the analog board, which happens to be where the power supply is,
which is why the board swappers call it a power supply failure -- never
trust a man who believes that board swapping is a repair to give you
technical information).  I've had two flybacks fail on one of my Macs,
the early boards used one that tended to break down under heat and short.

>So far this condition hasn't affected performance in any noticeable way,
>but I find the noise so irritating that I have to shut the system down
>in order to stay in the same room.  I'm also getting reluctant to leave it
>on when I'm not at home for fear of finding charred remains when I return...

Yes, I'd probably find a good repair depot (look at MacTutor for a place
that repairs boards, not swaps them).  The first time my Mac died, it cost
me lots for a board swap.  The second time my Mac died, it cost me $40 for a
new flyback.  It's been solid since then.  Of course my second Mac seems to
have a cold solder on the video, but I'm going to take a look at that in a
week or so when my memory upgrade shows up.  For details on Mac's and cold
solder joints, read MacTutor...

>Anybody have a similar experience?  I don't have a fan - should I?  Would
>this cure it or just postpone the inevitable?

You want a fan.  All Mac Users, read my lips. YOU WANT A FAN.  Sticking a
fan on your Mac can drop the internal temperature significantly.  While the
Mac may be within spec (if you've put anything INSIDE the box, however, it
isn't) it is at the high end of the spec.  Lowering the temperature reduces
the stress on the components, which can only make them better and more
reliable. I use the Kensington, which moves the powerswitch up front (which
is good, because I use enclosed computer desks) and also has a surge
supressor.  But any fan is better than no fan.

chuq
Chuq Von Rospach	chuq@sun.COM		Delphi: CHUQ

Now, where did my ex-wife put my Fairy Dust?