Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ub.d.umn.edu!cs.umn.edu!ux.acs!clarson
From: clarson@ux.acs.umn.edu (Chaz Larson)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Mac temperature, fan, dust.
Message-ID: <2135@ux.acs.umn.edu>
Date: 24 Aug 90 21:25:22 GMT
References: <9013@ur-cc.UUCP> <6910N3w162w@tosh.UUCP> <9053@ur-cc.UUCP> <2125@ux.acs.umn.edu> <8999.26d534ec@rsmas.miami.edu>
Reply-To: clarson@ux.acs.umn.edu (Chaz Larson)
Organization: Iron City, USA
Lines: 50

In article <8999.26d534ec@rsmas.miami.edu> miller@rsmas.miami.edu writes:
>[ in response to my theory of why a reversed fan would heat a Mac IIcx
>instead of cooling it, a fine explanation of the actual physics of the
>matter]

OK, here's what I was thinking.  The internal layout of the IIc- is:

<pardon the lame ascii graphics>

               fan
               vv	
   __________________ 
   |         |    | |
   |         |____| |
   |         |      |
   |         |      |  <power supply
   |         |______|
   |                |
   |                |
   |                |
   |                |
   |________________|


Now, I had assumed that the power supply would be one of the hottest 
components inside the case.  Normally, the air is drawn through the case,
where it "absorbs" some of the heat produced by the motherboard, etc., then
is drawn across the power supply just before it is exhausted.

If the fan is reversed, it blows air across the power supply, where [I had
figured] it would pick up a lot of heat, which would reduce the air's
ability to "absorb" motherboard, etc. heat, resulting in an increasing
internal tenperature.

All that said, however, I currently have my IIci open as I type this, and
I find by poking around that the power supply is one of the coolest 
things in this box.  various other parts, including the hard drive and 
some silver-jacketed boxes on the motherboard, are much warmer.

So, I'm insane.  Pardon my interruption and never mind.

chaz



-- 
--
 Joan Rivers Slaughters Ninety-Five Chinese Physicists in drunken rampage.
                 			 -spew
clarson@ux.acs.umn.edu                                       AOL:Crowbone