dmg@ssc-vax.UUCP (David Geary) (03/05/88)
I am interested to know, from a TECHNICAL viewpoint, whether or not it causes any damage to turn a PC off everyday. Personally, I have an Amiga which I leave on ALL the time. However, here at Boing, we are supposed to turn off all pc's every night to save electricity. This strikes me as a stupid idea, because I believe that it will damage the monitor after an extended period of time. Also, we have workstations, which occasionally get turned off by well-intentioned people who think they are pc's, and thus loose everything on disk... Anyway, I'd like someone to send me a technical explanation (not - "Oh I think it's a bad idea to turn them off") of why it is or isn't a good idea. Thanks, -- *********************************************************** * David Geary, Boeing Aerospace Co., Seattle, WA * * I disclaim all disclaimers.... * ***********************************************************
Oliver@cup.portal.com (03/07/88)
Well this is one of those subjects that gets ripped apart ever year or so... I know in the mainframe and super micro world the word is leave em on unless you need to replace the guts.... I have heard from engineers that it saves the power supply from the nnasty surge on the rectifiers when the system powers up. (filter caps do draw a lot of juice on some big supplies). Although I am not shure.. I would think that hitting IC's with voltage from startup whan they are at ground potential everyday would do something... I know for a fact that big disk packs love to run round the clock and Burroughs says "Leave them pups running"... Thats my 2 cents worth (what ever that comes out to after FCC tariafs I'm not shure.... Oliver@cup.portal.com P.S. I'm a lonely Bellingham resident...Any jobs at Boeing for a deticated computer tech? (Just had to throw that sales pitch in..Just had to..)
adrian@cs.hw.ac.uk (Adrian Hurt) (03/07/88)
In article <1727@ssc-vax.UUCP>, dmg@ssc-vax.UUCP (David Geary) writes: > I am interested to know, from a TECHNICAL viewpoint, whether > or not it causes any damage to turn a PC off everyday. > > Personally, I have an Amiga which I leave on ALL the time. > However, here at Boing, we are supposed to turn off all ----- Is that their new nickname? :-) > pc's every night to save electricity. This strikes me > as a stupid idea, because I believe that it will damage > the monitor after an extended period of time. Also, > we have workstations, which occasionally get turned > off by well-intentioned people who think they are > pc's, and thus loose everything on disk... You may damage the monitor if you turn it off and on frequently, i.e. once every couple of seconds. You may also damage the monitor by leaving it on continuously, and don't give the EHT circuits a rest. For one thing, if there is anything on the screen, it will eventually get burned onto the phosphor. Here, ever since our old Televideo terminals started blowing capacitors on the monitor boards (despite circuitry which turns off the display if inactive) our policy has been, turn the terminal off when not in use. This has not resulted in any harm, and the terminals haven't blown their capacitors in a long time. One exception is the console terminal of a multi-user Sun system; if that is turned off, it causes the system to crash! Fortunately, the terminal isn't a Televideo, and hasn't suffered from being left on (yet). -- "Keyboard? Tis quaint!" - M. Scott Adrian Hurt | JANET: adrian@uk.ac.hw.cs UUCP: ..!ukc!cs.hw.ac.uk!adrian | ARPA: adrian@cs.hw.ac.uk
dab@ftp.COM (Dave Bridgham) (03/08/88)
With powering off PC's, one of the important things to consider is the thermal cycling of the picture tube filament. I havn't read of any studies with picture tubes, but I have with with flourescent lights. Many places leave their lights on all the time on the belief that this prolongs their life. It was found that this is not necessarily the case. If the lights are on continuously for 10 hrs a day and off the rest of the time, they lasted longer than if they were left on 24 hrs a day. I'm not sure how well the results of the lights study transfers to picture tubes, but the problem is basically the same. The other thing I would be concerned about is spinning up and down hard disks. This is when most head crashes occur. I don't have any hard information about that though. David Bridgham
csg@pyramid.pyramid.com (Carl S. Gutekunst) (03/08/88)
In article <1727@ssc-vax.UUCP> dmg@ssc-vax.UUCP (David Geary) writes: >I am interested to know, from a TECHNICAL viewpoint, whether >or not it causes any damage to turn a PC off everyday. This is a religious war that comes up anually.... Here's one engineer's view: In general, electrical equipment functions most reliably when it's power and temperature are constant. There is a laundry list of components and subsystems that can be damaged by changes: stresses from thermal expansion and contrac- tion (and resulting misalignment of critical parts, like disk drive heads); surge voltages into the MOS components; surge currents into the power-supply components and CRT filament; wear on bearings of rotating parts (fans). Of course, leaving a CRT on does no good if you don't crank the screen intensity down whenever you have a constant display.... All of which suggests that, yes, you should leave the equipment on all the time, if you have a stable and spike-free line power. That's a critical "if." At home, I *do* turn my computers and other electronic equipment off after use, because of the poor quality of incoming electrical power. Better to have the clean, controlled power-cycle of the "off" switch than the erratic surges coming in over the power lines. The exception: I leave my terminals on, with their temperature-sensitive CRTs. >However, here at Boing, we are supposed to turn off all >pc's every night to save electricity. We had a similar policy at Burroughs. It was overturned when an engineer in the terminals division proved that the increased maintenance cost of a power- cycled terminal exceeded the electricity cost by a factor of 10. This was in 1979, when CRT terminals cost twice as much as they do now, and electricity cost half as much. But consider this: a typical terminal only costs $65 per year to run continuously, versus $15 per year to run during business hours. That means that if only one out of every ten terminals fails during the year because of power cycling, you've wiped out your cost saving. I would estimate that, for terminals, the number is much higher than one in ten per year. Our lab has about 20 minicomputers in it. All have conventional Wyse, Ampex, AT&T, and Espirit console terminals. Some (on the production systems) stay on all the time. Others (on test systems) get power cycled a lot. The difference is striking and aggravating -- aggravating since we're constantly having to find replacement terminals for the test systems. <csg>
Howeird@cup.portal.com (03/08/88)
>dme@ssc-vax,UUCP (David Geary) asks if it does any damage to turn > a PC off at night As a technician with 10 years in the field (yes, there WAS electronics before PCs), I can assure you that no damage is done to a PC by turning it off for the night. However, there are some long-term decisions involved here. Here's the trade-off: Passive electronic components, and I mean passive in the mechanical sense, not in the digital electronics sense, are stressed each time they undergo a heat change. So turning your PC off and on stresses the components. However, they also are stressed by the application of heat, so since keeping the machine on all night means keeping the components hot all night, you actually decrease the life of the machine by keeping it turned on. So the question is, which does the worst damage--leaving the machine on and letting it stay hot all night, or turning it off and stressing the chips? Most engineers I deal with tell me that as a rule of thumb, if the PC is not going to be used for 8 hours or longer, turn it off. IF YOU HAVE A HARD DRIVE, you can change that to 3 hours. The reason is it takes a lot out of that hard drive motor's life to keep it spinning--much more than the spin-up and spin-down cycles. Also, ALWAYS park the heads on drives which are not self-parking. A couple of things to remember about turning the PC off for the night: If you are attached to a network of any kind, LOG OUT first. Back up your files. Like airplanes, PCs tend to crash and burn the most on takeoffs & landings. If your monitor has a separate power switch, don't forget to turn IT off, too. hope this helps. =================================================================== | Howeird@cup.Portal.com |The opinions expressed here are | | Sysop, Anatomically Correct BBS |a figment of your warped | | (415) 364-3739 |imagination. | ===================================================================
friedl@vsi.UUCP (Stephen J. Friedl) (03/08/88)
In article <16473@pyramid.pyramid.com>, csg@pyramid.pyramid.com (Carl S. Gutekunst) writes: > In article <1727@ssc-vax.UUCP> dmg@ssc-vax.UUCP (David Geary) writes: > >I am interested to know, from a TECHNICAL viewpoint, whether > >or not it causes any damage to turn a PC off everyday. > > This is a religious war that comes up anually.... Here's one engineer's view: > [various good comments about not turning terminals off] At an office it probably doesn't matter, but if in a residential area you might want to make sure your equipment isn't trashing your neighbor's TV. I would prefer to leave my terminal and modem on all the time but interference is really bad and I like to be a good neighbor. Just one more thing to think about... -- Life : Stephen J. Friedl @ V-Systems, Inc./Santa Ana, CA *Hi Mom* CSNet: friedl%vsi.uucp@kent.edu ARPA: friedl%vsi.uucp@uunet.uu.net uucp : {kentvax, uunet, attmail, ihnp4!amdcad!uport}!vsi!friedl
csg@pyramid.pyramid.com (Carl S. Gutekunst) (03/08/88)
In article <120@ftp.COM> dab@ftp.COM (Dave Bridgham) writes: >I'm not sure how well the results of the [flourescent] lights study transfers >to picture tubes, but the problem is basically the same. No similarity whatsoever. A flourescent light heats its filament only during startup; in operation, it is a gas discarge tube. A CRT filament burns contin- uously, but at a lower temperature than the flourescent uses during startup. But your comment is correct: the stress on the filament of the CRT is not as significant a factor as others, e.g., surge voltages to MOS components. I do not ever recall seeing a terminal that had failed because of a burned out CRT filament. <csg>
pjh@mccc.UUCP (Peter J. Holsberg) (03/08/88)
There's another aspect to consider, in favor of turning computers off.
Components do not have infinite life -- especially disk drive bearings
and other mechanical thingies --, so turning systems off will help
preserve the life of these components.
Personally, I leave my 3b1 and 3b2 computers on all the time, and turn
off my PC clone at night. So far, I've had to replace one monochrome
monitor on the clone.
--
Peter Holsberg UUCP: {rutgers!}princeton!mccc!pjh
Technology Division CompuServe: 70240,334
Mercer College GEnie: PJHOLSBERG
Trenton, NJ 08690 Voice: 1-609-586-4800mjy@sdti.UUCP (Michael J. Young) (03/09/88)
In article <120@ftp.COM> dab@ftp.COM (Dave Bridgham) writes: > > With powering off PC's, one of the important things to >consider is the thermal cycling of the picture tube filament. I >havn't read of any studies with picture tubes, but I have with with >flourescent lights. Many places leave their lights on all the time on >the belief that this prolongs their life. It was found that this is >not necessarily the case. If the lights are on continuously for 10 >hrs a day and off the rest of the time, they lasted longer than if >they were left on 24 hrs a day. I'm not sure how well the results of >the lights study transfers to picture tubes, but the problem is >basically the same. The analogy of florescent lights is an appropriate one. Turning florescent lights on and off may indeed shorten their effective life. But that doesn't mean it's cost-effective to leave them on. For example, say you have a light that has a rated lifetime of 1000 hrs. Cycling the power once a day as suggested above shortens its lifetime by 30%. But the light is only needed 10 hours a day. The other 14 hours, there is nobody around to care if the light is off or on. Then the USEFUL life of the light that is left on continuously is only 10/24, or 42% of 1000 hours. The total number of useful days of light is only: 1000 hr/day ----------- = 42 days 24 hr/day But the light that is cycled each day has a USEFUL life of: 1000 hr * .70 ------------- = 70 days 10 hr/day In effect, the light lasts longer because it is turned off and on, even though it technically isn't "good" for it. The same can be applied to computers, disks, and CRTs. I've never heard of real studies to see what the actual numbers might be, though. > The other thing I would be concerned about is spinning up and >down hard disks. This is when most head crashes occur. I don't have >any hard information about that though. On the other hand, leaving the disk on could result in increased wear on the bearings. I doubt if this is much of a concern, though. With all that said, you might think I turn my computer off at night. Actually, it runs 24hrs/day, since I get my news feed at night. -- Mike Young - Software Development Technologies, Inc., Sudbury MA 01776 UUCP : {decvax,harvard,linus,mit-eddie}!necntc!necis!mrst!sdti!mjy Internet : mjy%sdti.uucp@harvard.harvard.edu Tel: +1 617 443 5779
richard@calvin.EE.CORNELL.EDU (Richard Brittain) (03/09/88)
Just to throw in one more perpective, friends of mine operated a PC
in a study-bedroom continuously for about 6 months, on the advice that
it was better for the machine to be left on. This is not an unusual
situation for students, and the average student bedroom is a lot dustier
than the average office. When they enlisted my help to open it up and
install a new graphics card, I _peeled off_ the carpet of dust/hair/fluff
from the mother board. Miraculously it didn't seem to have caused any
problems at all, but after that they started turning it off so that the
fan wasn't continuously 'vacuuming' their bedroom.
--
Richard Brittain, School of Elect. Eng., Upson Hall
Cornell University, Ithaca, NY 14853
ARPA: richard@calvin.ee.cornell.edu
UUCP: {uunet,uw-beaver,rochester,cmcl2}!cornell!calvin!richardroy@phri.UUCP (Roy Smith) (03/13/88)
dmg@ssc-vax.UUCP (David Geary) writes: > I am interested to know, from a TECHNICAL viewpoint, whether > or not it causes any damage to turn a PC off everyday. Here's some of the things that I've heard are bad about turning computers on and off every day. I've never seen hard experimental evidence that these are true, but they all make a lot of sense from an engineering point of view. 1) Thermal cycling of CRT filaments. When a filament gets hot it expands and when it gets cold again it contracts. The thermal cycling leads to mechanical stresses on the filament which cause it to break. Tungsten (which I assume CRT filaments are made of) has a negative thermal coefficent of resistivity, meaning a filament has a lower resistance when cold than when hot; that translates into large inrush currents when you first turn a CRT on (i.e. before the filament gets hot). Decent CRT designs will have some sort of current limiting, but it's not 100% effective. Over the past few years, there have been extensive discussions of light bulb life on the net; if you can find those old articles somewhere, I'm sure a lot of what was said applies to CRT filaments as well. Thermal cycling, to a lesser extent, will also cause damage to solder and contact connections. 2) Power supplies. When a power supply is turned on, it may take some time for the output to stabilize; before then, it is putting out some strange voltage. CMOS may not mind running off of a variable power supply, but TTL does strange things on 1.5V, especially if you've got several supplies and some have come up to rated voltage before the others do. You may see abnormally high transient currents. Even if the power supply stays strictly within the range from 0 to its rated output, the intermediate voltages in between may do strange things to the logic circuits. 3) Disk drives. When you power down a disk, the heads have to land (yes, I know not all disks have landing heads, but most small winnies do). While landing on a dedicated landing zone is better than landing on some random part of the disk, its better not to land at all. When you power up again, you get big inrush currents in the drive motor until it gets up to speed. On the flip side, every hour your PC is powered off is one less hour it's exposed to potential power-line uglies. With any kind of decent surge protection, though, I'd say that this is of pretty minor significance. If, on the other hand, you know that you routinely get massive surges in the middle of the night, it might be worth considering. If you've got a large number of PCs (like 100), you may be in a good position to do a controlled experiment. Pick half your PCs at random and turn them off every night. Leave the other half on. Keep careful records of repairs. At the end of, say, 6 months, sit down and work up some stats. Then, do the entire net a very big favor and let us all know how things work out. -- Roy Smith, {allegra,cmcl2,philabs}!phri!roy System Administrator, Public Health Research Institute 455 First Avenue, New York, NY 10016
swd@micas.UUCP (swd) (03/15/88)
In article <1734@brahma.cs.hw.ac.uk>, adrian@cs.hw.ac.uk (Adrian Hurt) writes: > One exception is the console terminal of a multi-user Sun system; if that is > turned off, it causes the system to crash! Fortunately, the terminal isn't a > Televideo, and hasn't suffered from being left on (yet). > > Adrian Hurt | JANET: adrian@uk.ac.hw.cs > UUCP: ..!ukc!cs.hw.ac.uk!adrian | ARPA: adrian@cs.hw.ac.uk The Sun I'm using now (3/160 running 3.2EXPORT doesn't, probably doesn't have time to with crashing due to lack of disc space, static electricity ... :-} Steve Day
mfineman@cadev4.intel.com (Mark Fineman) (03/15/88)
I have had 7 out out 120 terminals smoke (yes - literally smoke)
in the last year. I also had 2 terminal servers (out of about
30) smoke on attempt to install in the last year.
From long experience in the computer and electronics
industry I have seen many cases of improper circuit protection
devices. I've even had two home TV's catch fire, but these were in
in 1951 and 1958 respectively, so I don't count them now.
I had a case recently where the field service guy said I should
leave a particular model of his company's terminals (admitedly
7 years old) on since "the power supply was flakey" - right!
I have maintenance agreements for all terminals, PC's, printers,
terminal servers, etc.
I have my laser printers and terminal servers in a room with
automatic sprinklers.
I have about 10 GPX's in office areas. I keep these on all of
the time. I have not had any problems with them, but they
still worry me. I try to get people to turn off the color monitors,
since these are the things that worry me most.
I tell everybody to turn off all monitors at night.
I have had numerous falures of disks and computers after power
shutdowns, so I don't bug people to turn off PCs, only their
monitors.
Summary:
1. Get service contracts on everything
2. Do good backups
3. Have good procedures for bringing up new terminals,
PC's, disks, backups.
4. Turn everything off when both not needed and not attended.
This gives you a predictable failure rate and no catastrophies -
One PC failure everyother week out of 100 PC's is painless to
recover from, one fire in 5 years wiping out 20 PC's and 20
offices would be very painful to recover from.
(408) 765-4277; MS SC3-17, 3065 Bowers Ave, Santa Clara, CA 95050
/ decwrl \
| hplabs |
-| oliveb |- !intelca!mipos3!cadev4!mfineman
| amd |
\ qantel /terry@wsccs.UUCP (terry) (03/15/88)
In article <1734@brahma.cs.hw.ac.uk>, adrian@cs.hw.ac.uk (Adrian Hurt) writes: > Here, ever since our old Televideo terminals started blowing capacitors on > the monitor boards (despite circuitry which turns off the display if inactive) > our policy has been, turn the terminal off when not in use. This has not > resulted in any harm, and the terminals haven't blown their capacitors in a > long time. At WSC, there were a number of explosions of Televideo terminals (the old 912c's, to be exact), traceable to capacitors on the monitor boards. This was corrected (it was thought) by replacing the capacitor that was on the board (a _polar_ capacitor) with a non-polor capactior, as it was documented in the original specs. This seemed to clear up the problem... until some time later when >*BOOM!*<; another terminal goes to terminal heaven. When the building got conditioned power, we thought that was the end of it. >*BOOM!*<, another one went, within a week of the power conditioning. Moral: Don't use the same power line for your Televideo terminals as you do to send the 50v synchronization pulse from your centralized clock system! :-) terry@wsccs
mlinar@eve.usc.edu (Mitch Mlinar) (03/15/88)
In article <3174@phri.UUCP> roy@phri.UUCP (Roy Smith) writes: >dmg@ssc-vax.UUCP (David Geary) writes: >> I am interested to know, from a TECHNICAL viewpoint, whether >> or not it causes any damage to turn a PC off everyday. > > On the flip side, every hour your PC is powered off is one less hour >it's exposed to potential power-line uglies. With any kind of decent surge >protection, though, I'd say that this is of pretty minor significance. If, >on the other hand, you know that you routinely get massive surges in the >middle of the night, it might be worth considering. There is a bit more to this than just turning it off. You need protection against massive surges caused by power-line drop-out/reactivation due to lightning or one of those mylar balloons hitting a power pole. During last year, my close community of friends lost 2 PCs during an electrical storm and another during a "mylar balloon attack". All were plugged in, had surge protection, AND WERE OFF!! If you see an electrical storm coming, unplug your computer. Mylar balloons are another problem (use a shotgun or missile launcher? :-) :-)). -Mitch
todd@uop.edu (Dr. Nethack) (03/17/88)
In article <239@calvin.EE.CORNELL.EDU>, richard@calvin.EE.CORNELL.EDU (Richard Brittain) writes: > When they enlisted my help to open it up and > install a new graphics card, I _peeled off_ the carpet of dust/hair/fluff > from the mother board. Miraculously it didn't seem to have caused any > problems at all, but after that they started turning it off so that the > fan wasn't continuously 'vacuuming' their bedroom. Go to a hardware store and pick up those trimmable air filters for an air conditioner, or some polyesther batting, make a filter!! ----------------------------------------------------------------------- + uop!todd@uunet.uu.net + + cogent!uop!todd@lll-winken.arpa + + {backbone}!ucbvax!ucdavis!uop!todd + -----------------------------------------------------------------------
ncreed@ndsuvax.UUCP (Walter Reed) (04/02/88)
In article <1727@ssc-vax.UUCP> dmg@ssc-vax.UUCP (David Geary) writes: > >I am interested to know, from a TECHNICAL viewpoint, whether >or not it causes any damage to turn a PC off everyday. It isn't turning them off, it's turning them on :-) What happens is that a surge of power courses through the machine when it is turned on. For a brief period of time, a high amount a current charges capacitors and can strain other components. I have heard that this can shorten the life of equipment. It is cheaper and more reliable to leave the equipment on than to repair or replace it. > >Personally, I have an Amiga which I leave on ALL the time. Good choice of machine :-) I also leave my amiga on all the time. >* David Geary, Boeing Aerospace Co., Seattle, WA * -- /* Walter Reed UUCP : uunet!ndsuvax!ncreed Internet : ncreed%NDSUVAX.BITNET@CUNYVM.CUNY.EDU Ph 701-235-0774 Bitnet : ncreed@ndsuvax OR NU105451@NDSUVM1 ------------------- */
markz@ssc.UUCP (Mark Zenier) (04/05/88)
If you live in thunderstorm country, the chance of getting your computer fried by a power glitch outweighs the reduction in life caused by turning it on once a day. Its a tradeoff on the wear and tear on your hard disk running 2 or 3 times as as many hours, versus the startup. I powered down a PDP-11 every day for 4 years and didn't fry it. Mark Zenier, holder of the Cliff Claven chair in the school of unsubstantiated opinion.