21 Oct
2005
21 Oct
'05
2:16 p.m.
Subject: Fan Direction (was: Re: PC floppy cable twists...)
From: Mark Tapley <mtapley at swri.edu>
Date: Fri, 21 Oct 2005 13:24:57 -0500
To: cctalk at classiccmp.org
At 6:09 -0500 10/21/05, Allison wrote:
That would be a bad thing.
.... All of my systems
cooling and air flow get attention even if it requires some card stock
and tape duct work. Fans blow in and filters keep cat hair and
other deutrius from getting in those places where it's going to do bad
things. I find that tends to keep the inside of my PCs clean too. I
turn the fan around and add a filter. Beats having a hairball clogging
the cpu fan and crashing the system.
<see my previous posting, somewhere back in the archives...>
Although this in general is a good idea, it doesn't always
work. NeXT cubes were designed with the fan exhausting air, so the
crapola sucked in through the optical drive slot wiped out the
optical drive before long. NeXT eventually approved the procedure to
mechanically turn the fan around (do *NOT* simply reverse the
connector). Problem is the designers actually did do _some_
thinking. On
its way out the fan in the original configuration, the air went over
the logic board(s) first, then the power supply and drives last.
Reverse the fan, it's now hot air hitting the logic board. On my
system, this caused the SCSI controller to fail occasionally.
Solution in my case was to put the fan back to its original
configuration, then tape over the floppy and optical cut-outs on the
front of the case. (N.B. my system may be unique in that the floppy
is mounted with a custom mount to an optical-sized cutout, with no
attempt to seal well. It may be that either taping or reversing the
fan would have solved the problem.)
--
Before I did it there was some thought applied and a few changes like
an added fan in a differnt location. In the end I was both pressurizing
the case and insuring adaquate airflow over the hardware.
In the case of most PCs the airflow pattern is at best bad and its
difficult to make even small improvements. But some of the S100
cases the airflow was poor to non existant. In those trying to get
a laminar airflow or even air to flow between the boards in a crowded
case was hard to achive. The worst is any of the altairs, one look
and you see why.
Allison