From: tomfox@cs.utexas.edu (Thomas Y.C. Woo)
Newsgroups: comp.terminals
Subject: Summary: Leaving Terminals on
Date: 27 Jan 1993 11:40:17 -0600
Organization: CS Dept, University of Texas at Austin
NNTP-Posting-Host: needmore.cs.utexas.edu
Keywords: terminals


Sometime back, I posted the following question:

>
>I have a question regarding terminals. I have noticed that most
>terminals are always left on around the clock. I want to
>know if this is in fact better for the terminals, instead of
>turning them on and off every time they are used. By better,
>I mean for them to last longer.
>
>The terminals I am talking about all have automatic blank
>out feature. So leaving them on would not leave burn on the
>screen.
>

Here is a compilation of all responses I have received. Thanks for
everyone who has responded.

Regards,
Thomas Woo
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The number of power cycles has a definate effect on the life of an electric
the multitude of users that we have, less trouble and better
performance occurs when they are left on all the time. With a single user
and a few hours use, it is probably better to turn them off between use.
I turn my personal equipment off when not in use.  No hard and fast rule
can be made.  It is pretty much one's own decision in relation to the
situation.

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The question of whether to turn things off and on has been around since
computers were invented.  Basically, it comes down to a toss up.  By
leaving things on they are at a nearly constant operating temperature which
decreases thermal expansion failures of the bonds inside components. 
Turning things off cuts down on the dopant migration within the semiconductors
and drying out (heat degradation) of insulators and passive components.
Some components fail when turned on because of the higher than quiescent
current surges that occur when power is applied.

------------------------------------------------------------------

As long as you're not burning out the phosphor, which
it sounds like you're not, then it *is* better to leave
them on.

Changing the power level on a regular basis will eventually
wear out the electronics.  It uses only slightly more power
to just leave them on 24-hours a day, and they will last years
longer.

The old concern used to be that your screen burned out, but
you could manually turn the intensity level down, too.

Same goes for a PC or a Sun or any other computer.  If you leave
it on all the time, it will last longer.  Starts and stops are
what wear it out more than anything else.

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Since multiple "no" answers have been posted, I feel compelled to post
this one also.  Which is that *some particular models* of terminal are
best left on.  In particular, most of the terminals here at SoftQuad a few
years ago were HDS 200's, and their power supplies would fail regularly.
We did an experiment where we left all the terminals on all the time in
half of the office, and the power supply failures stopped in that half
and continued in the other half.  We felt this was sufficiently conclusive
to have all the HDS 200's left on all the time, and while the failures
did not quite stop altogether, they became a lot less frequent.

Terminals that do not have that sort of flaw, though, probably do better
to be turned off.

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I've always been told, by our engineers, its better to leave them
on reason being that there is more of a chance to wear out a component
or burn one out at the time of power up.

I'd be interested to see your compilation of responses if you get
enough that make sense.  Others might find it interesting as well.
If you're so inclined, please post something in comp.terminals on
what the general consensus is.

------------------------------------------------------------------

This has been discussed a number of times. You'll find experts
who can _prove_ that terminals that are switched off overnight
will last longer. You can also find experts who can _prove_
the opposite.

US-Americans tend to leave them on, most others switch off overnight.

Try to guess why the US have a much higher per-capita power consumption
than every(?) other country.

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It all depends on the specific terminal.  Turning on electronic equipment
usually causes a transient surge current as capacitors charge up, etc.,
which can be more stressful than continuous operation.  On the other hand,
operating equipment dissipates heat and sometimes the heat gradually
damages components.  (In an ideal design it shouldn't, but for economic
reasons some compromises are oftne made.)  Phosphor degradation is a big
concern but automatic screen blanking should make that a non-problem.
The one remaining problem is that the filament of the CRT will gradually
degrade, shortening expected life of the CRT.  Whether this is worse than
jolting the filament by turn-on thermal surges as it rapidly heats up I
don't know.  Personally if it is a decent model I'd turn it off when not
in use.

------------------------------------------------------------------

I heard a long time ago that HP had done a study on this and 
they found out that turning terminals off at night saved electicity
and burned the filaments less time but that the thermal shock
of starting the tube actually shortened tube life.  They found out
that everything almost exactly balanced out, so it doesn't make
any difference what you do.

Good Luck.

Newsgroups: comp.terminals