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From: qman@casbah.acns.nwu.edu (Charlie Kuehmann)
Subject: Re: Monitors - should they be kept on 24 hours a day???
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References: <1r3jl5$igh@function.mps.ohio-state.edu> <C5uHHI.2HDG@austin.ibm.com>
Date: Wed, 21 Apr 1993 21:42:44 GMT
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In article <C5uHHI.2HDG@austin.ibm.com>, kelleyb@austin.ibm.com (Kelley
Boylan) wrote:
> 
> 
> > Yes, I know computers and harddisk drives should be ALWAYS on. But what about
> > monitors? They generate a lots of heat. Should I or shouldn't I keep them on
> > 24 hours a day? Any advice? Thanks. Take care...Paul
> 
> There has been no empirical evidence to support the first statement.  True,
> there is a power surge at startup that has the potential to do damage, but
> the internal power supply is well-protected. (I've turned my Mac on and off 
> six or seven times a day for three years without problem).  The monitor is
> the same.  To leave it on is to waste a lot of electricity -- twice as much
> as a television, possibly more.
> 
> Turn it off when you're not using it.  It'll save you money and the world
> a few more resources.

The problem with turing your computer on and off constantly is not due to
the power surge at start up.  It is due to thermal fatigue.  You turn on
your computer, it heats up, and everything expands.  You turn it off, it
cools off, and everything contracts.  There is a limited number of cycles
of this that any component can take before it fails.  Modern electronics
are much more robust in this respect than their predeccesors.  In fact
portable computers are designed with this in mind since the sleep function
that extends battery life also greatly increaces the number of thermal
cycles that occur.  As a rule of thumb, if I am not going to use my
computer (and this includes the monitor) in the next 4-6 hours, I turn it
off (I always dim the monitor when not in use to prolong the life of the
phosphor).  I tend to think that with the pace of technical innovation in
the computer industry you should be much less concerned with the fatigue
life of your equipment and more concerned with how long your particular
architecture will be supported by hardware and software vendors. :") 

Charles Kuehmann
Northwestern University
Steel Research Group
