hans@Shasta.STANFORD.EDU (Hans Mulder) (01/07/87)
Recently I had a discussion at a local computer store about power surges and other uncleanliness on the wall(AC) power. They claimed that some of my problems with my harddisk (4 defects in 6 months) were due to dirty power and that I should immediately buy a surge suppressor. They basically claimed that the wall power is so bad that it can destroy power supplies (and other parts of a computer). I have serious doubts about their claim because of: 1. Bad power can effect a computer twofold: 1. it makes the computer crash, and/or corrupts data; 2. and/or it damages the computer. Although it is arguable that these two effects are not hierarchical, I find intuitively that if my Mac doesn't crash it is unlikely that it gets damaged. My Mac rarely crashes or corrupts data for no reason. 2. It is not only computers which have complicated sensitive power supplies. Does it mean that surge suppressors are needed for CD players, computerized stereo equipment, etc, etc? Because those power supplies need to be less reliable, aren't they more likely to be damaged? 3. If the store is right why don't hard disk manufacturers build-in filters, suppressors etc. I doubt that they can invalidate the waranty on the drive when it brakes because you don't have a surge supressor. Given the fact that my Mac rarely crashes because of unknown reason, do I need a surge supressor or not? If I need one what are the important facilities it should have? Are there ones which switch of the power in case of power dips (something I can see the use of)? All answers, and pointers (to articles) appreciated. Hans Mulder ARPA: hans@umunhum.stanford.edu UUCP: shasta!hans
oster@lapis.berkeley.edu (David Phillip Oster) (01/07/87)
If you remember MacWorld Vol.1#1, you'll remember there ewas a discussion of the mac hardware in that issue. You can see the surge protector on th Mac boards. I've been in a room with 3 Macs and 2 Lisas, and watched a power glitch crash the Lisas without touching the Macs. The Mac is simply better than most computing equipment when it comes to coping with real world power. However, surge protection is done with a circuit element called a MOV. The problem with MOVs is that for every surge they suppress, they wear out a little. Eventually, they are all used up and nobody has a cheap tester to tell you when you should replace yours or augment them with an extra surge protection box. Steve Ciarcia had a long article discussing surge protection a few years ago in Byte magazine. It gave tips for building your own surge suppressors buy buying your own MOVs and soldering them into your extension power strips. --- David Phillip Oster -- "The goal of Computer Science is to Arpa: oster@lapis.berkeley.edu -- build something that will last at Uucp: ucbvax!ucblapis!oster -- least until we've finished building it."
shap@sfsup.UUCP (01/10/87)
In article <1094@Shasta.STANFORD.EDU>, hans@Shasta.STANFORD.EDU (Hans Mulder) writes: > > Recently I had a discussion at a local computer store about power surges > and other uncleanliness on the wall(AC) power > They claimed that some of my problems with my harddisk (4 defects in 6 months) > were due to dirty power and that I should immediately buy a surge suppressor. > They basically claimed that the wall power is so bad that it can destroy > power supplies (and other parts of a computer).... Indeed wall power is horrible, and its quality depends a lot on what block you are on and which power trunk and the phase of the moon and the quality of your local power station and the current price of tea. It is possible for electricity to do oddball things, like blowing out little used portions of, say, a ROM. You won't konw until you need it. It is also easy for an unprotected computer to be turned into so much charred plastic and metal by a vagrant electrical storm. There have been several such tales of woe on the net over the years. The same holds for VCR's, Televisions, and the like. Manufacturers do not tend to include this stuff by default because it costs money, and sites with more than a few machines often have their own power conditioning, and don't want to pay the extra money. Also, it is more profitable to let you replace your PC. As to the warrantee, electrical damage comes under acts of God, and usually warrantees do *not* cover these. There are two sorts of protection you need. The first is from spikes, which are instantaneous transitions of voltage on your power line which can go as high as five times the line's rating. These little jiggles can quite contentedly blow away silicon. The second is surges, which are of longer duration, though usually not as high. These can be caused by the time lag between the grocery down the street's industrial freezer kicking in and the power company putting more power on the net. It is a feedback process, so when the unit kicks out there will be too much power for a while. Either direction is a potential problem. Some dealers will tell you that these are the same thing. They are not. Electrically they have different properties and are prevented by slightly different circuitry (mainly, some capacitor and resistor values change). You probably want a unit with a circuit-breaker rather than a fuse. They cost a bit more, but it pays off the first time you would have needed to replace the power protection. I have had occasion to be thankful.... As to brands, I use the Apple/Lemon/Orange/etc.. series, which many dealers carry. I am sorry that I do not recall the manufacturer. It is about the cheapest insurance policy you can by. Not protecting your 3,000 dollars worth of computer equipment with a $30 surge suppressor is just plain foolish. Hope that helps a bit. Jon Shapiro AT&T Information Systems
eacj@batcomputer.tn.cornell.edu (Julian Vrieslander) (01/13/87)
Recently there was a comparative review of surge/spike protectors in one of
the IBM PC rags (sorry, I can't remember which one - they all look the same).
Quite a few (10-20?) devices were tested with simulated glitches, and the
article reported substantial differences in the effectiveness of the products.
Some units provided legitimate protection, some were worthless, and I remember
that there was at least one unit that INCREASED the risk of surge damage: it
caught on fire! The authors suggested that different types of components are
needed to protect against different types of power line disturbances (surges,
spikes, RFI, etc.) and that the better boxes contained a variety of devices: RLC
filtering, MOV spike absorbers, gas discharge cells, relays, etc.
One unit that was recommended was the Datashield model 100. This comes with 6
outlets, 2 of which are "super-filtered", and has a total capacity of 10 amps.
It also has a brown-out alarm, and a switch for manually resetting after it
trips out. The manufacturers claim that this allows you to avoid the burst of
dirty juice that often comes when the lines come back on after a power failure.
Price is about $75-100 (depending on source).
Feeling superstitious, I bought a couple for my lab. Do they work? I don't
know, but they haven't burst into flames yet.
--
Julian Vrieslander (607) 255-3594
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