Path: utzoo!attcan!uunet!husc6!uwvax!rutgers!ucsd!nosc!helios.ee.lbl.gov!lll-tis!ames!oliveb!olivey!gnome
From: gnome@olivey.olivetti.com (Gary)
Newsgroups: comp.sys.mac
Subject: Re: crash and burn!!!  Why no fuse?
Message-ID: <27429@oliveb.olivetti.com>
Date: 17 Aug 88 02:26:13 GMT
References: <561@calvin.EE.CORNELL.EDU>
Sender: news@oliveb.olivetti.com
Lines: 21

From article <561@calvin.EE.CORNELL.EDU>, by johns@calvin.EE.CORNELL.EDU (John Sahr):
> Because the transistor/diode switch would probably blow up faster than any
> fuse if it failed, it might be pointless to put even a $.50 fuse in the
> SE or Mac II...
> I am just guessing, based on what I've learned about these type of supplies.
> John Sahr (johns@calvin) [opinions expressed are my own alone]

Fuses are very good in preventing certain types of failures from
becoming fire hazards, but in general, they won't really protect
a hell of a lot in a computer system.  The semiconductors will
blow much faster than a fuse.
Don't forget, if I remember correctly, a fast-blow fuse will
blow in 1 minute at 200% overload, others are much tougher
to blow-out.  They're great for dead-shorts (impulse power >10x
the rated amount).

Even with this point of view, I still over-fuse anything I
have design responsibility on.  I also believe in power-supply
crowbar circuits -- a lot.

Gary