We learn Something Weird every day

Discussion in 'Computing' started by Mick, May 31, 2004.

  1. Mick

    Hunter1 Guest


    One beauty of XP, the multiple calls we used to get from
    that are fading away, the fucker actually warns them about
    caps lock! 8]
     
    Hunter1, Jun 4, 2004
    #21
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  2. Mick

    Unknown Guest

    I actually am thinking of stopping phone advice. I spent 20 mins on the
    phone with a guy I see now and then, solved his problem and got nothing for
    it. Been happening a lot with a lot of people! Might go back to "I can be
    there at...." instead! :)
     
    Unknown, Jun 6, 2004
    #22
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  3. Mick

    John Leister Guest




    I hate relatives that soon find out you can fix things and you never seem to
    stop the phone calls . And you can't really be nasty to family members
    which I find quite hard....

    Of course I suppose if I said give me $$$$$ they would soon shut the
    hell up and not phone.
     
    John Leister, Jun 6, 2004
    #23
  4. Mick

    John Leister Guest

    I think quite a few people would
     
    John Leister, Jun 6, 2004
    #24
  5. Sure, a direct hit will blow anything, but properly used, a half decent
    one will stop 95% of the damage, which is caused by a surge on power or
    phone lines from hits some distance away (maybe only 10s of metres
    though). A neighbour last wet scored a direct hit to a new carport. The
    computer and TV etc about 3 metres away survived - with surge protectors.
    In Darwin, if you unplugged everything at the first rumble you hear, you
    would hardly ever have it working for several months during the wet
    season. That is not practical. There are often electrical storms every
    day for weeks.

    People here use surge protectors, but unplug when the equipment is not
    being used. I have never seen equipment that has been destroyed when
    correctly plugged in via a surge protector, but I've seen lots of gear
    that fried because it wasn't. They are certainly 'worth the effort', but
    it cannot be assumed your gear is perfectly safe.


    Noel Bachelor noelbachelorAT(From:_domain)
     
    Noel Bachelor, Jun 6, 2004
    #25
  6. Mick

    Unknown Guest

    A properly installed lightning arrestor that is properly earthed will have a
    better chance, yep. A surge protector has none.
    Lightning is unpredictable. Power pole across the street from a guy I went
    to see. Killed some houses in the street including his but not the
    neighbours either side even though none of any of them that he knew had any
    sort of lightning protection. In his house, didnt kill everything either but
    seriously killed SOME things. You cant say a simple surge protector
    protected because it was there. If lightning surge chose to go that way, it
    would have blown those bastards easily. In fact it can arc out of the wall
    socket to a plug 6 inches from the socket if it wants (which I have known to
    be done at a work mate's house in 86). Lightning goes where it wants,
    really.
    So live around Wentworth Falls NSW and argue that point. It has the highest
    lightning strike incidence in the country and when there is no drought, you
    can spend all week just fixing blown modems and other parts. If you dont do
    it, you risk a lot of dollars and are being stupid with your data!
    Just because you havent doesnt mean it doesnt happen. Again, dont believe
    me - ask a qualified electrician.
     
    Unknown, Jun 6, 2004
    #26
  7. Mick

    Unknown Guest

    Not relatives, mate. Customers! This one I dont see all that often.
    Yeah well even with customers it gets funny. I had a guy asking me question
    after question and I answered quite a few then finally said "Look, I cant be
    sure of the answer to that one without seeing it so how about I come and
    have a look to be sure?" and he said "Oh but I would have to PAY you then".
    Now given I had never seen the guy before, I thought I wasn't being rude in
    just hanging up at that point....
     
    Unknown, Jun 6, 2004
    #27
  8. Nah, I'd reckon 99% of people who make those mistakes wouldn't even be
    aware this newsgroups existed.

    Noel Bachelor noelbachelorAT(From:_domain)
     
    Noel Bachelor, Jun 7, 2004
    #28
  9. 'Where it wants' is where it can find a path (or multiple paths) that will
    break down under the high potential gradient that it presents. Provide a
    low impedance path that bypasses your gear and the potential across your
    gear is greatly reduced. Lightning doesn't just jump at things and
    destroy them. It has to have a target path.

    However, virtually all electronic gear that gets 'hit by lightning' is not
    in the direct path of the lightning, but finds itself in the path of a
    surge that is induced into power or phone cables. These can destroy gear
    up to a few kilometres from where the lightning hits. Any cable not
    directly connected to ground can act as an 'antenna' and receive an
    induced surge from a nearby hit, and conduct it as far as it can until it
    finds a path to earth. Putting a surge protector across all the
    'external' lines to your gear provides that surge with a path that
    bypasses the internals of your equipment.

    Your gear does not have to be clamped to earth potential to survive. The
    potential at your gear can safely jump significantly relative to earth, as
    long as the equipment is not exposed to a differential mode surge (high
    voltage differences on different lines). A half reasonable surge
    protector (should) turn any differential mode surges to common mode
    (similar potential across all lines connected to it), so the electronics
    do not get exposed to higher voltages than they were designed for.


    Wentworth Falls? Get out of it. I've lived or stayed for significant
    periods of time all over Australia (and I can list quite a few places
    you'll need a good map to find). If you want to see a light show, spend a
    wet season in the top end. The area around Darwin has the highest
    lightning counts out. 'Hector', a huge thunderhead that forms and stays
    over the Tiwi Islands is mainly responsible. Meteorologists come here
    from around the world to study tropical storms because they are so regular
    and the mechanisms here are fairly well understood. Darwin has the only
    special purpose meteorological centre in Australia for that reason.

    I've seen maps of lightning counts from the Met bureau, and while there
    are a few other 'hot spots', Darwin shows up as the highest. See:
    http://www.bom.gov.au/climate/averages/climatology/thunder/tdays_light.shtml

    As I said, we gets lots of experience here, and equipment that survives
    more than one wet season is not just running on 'luck'.

    So why does every electrician and electronics tech in Darwin (myself
    included) strongly recommend people use surge protectors? I'm not sure if
    it has changed, but some years back, at least one insurance company here
    would not cover lightning damage to computers unless you had used a surge
    protector.

    I repeat, they are not 'useless' if properly used, and suggesting they are
    is likely to result in people deciding there is nothing they can do to
    protect their gear, other than unplug everything every time they turn it
    off, and for things that expect power availability all the time, that is
    not practical. I can only assume you like the income you make from
    repairing 'blown up' electronics.


    Noel Bachelor noelbachelorAT(From:_domain)
     
    Noel Bachelor, Jun 8, 2004
    #29
  10. Noel Bachelor said....
    I saw the aftermath of a mate's lightning hit recently. It hit the
    fence, melted the wire run that the dog was tied to (dog disappeared,
    never to be seen again), exploded an electric fence unit (plastic and
    electrical molten bits all over the backyard), and fried his TV, PC,
    microwave oven and cordless phone. PC was on a $100 surge protector, the
    others weren't protected.

    Dunno if the insurance paid to replace the surge protector. Probably a
    waste of money if it did. But all the other bits were repaired or
    replaced, as required.

    Prior to that, his modem was fried after lightning hit the phone line
    somewhere. Ever since then, the phone connection's been utter crap, and
    Telstra can't find the fault. Would probably have to replace about 400
    metres or more of copper in order to do so.
     
    Martin Taylor, Jun 8, 2004
    #30
  11. Mick

    Hunter1 Guest


    You're not kidding, lightning damage to equipment is pretty
    much always via path rather than direct strike, used to put
    up 100 foot metal towers out in the Timor sea for nav
    purposes, and there were more than one direct (presumably
    direct considering the damage done, and being the only thing
    over 10 or 20 foot high for hundreds of Km's it aint
    surprising, although the fact they weren't earthed makes it
    interesting) strikes on those towers in the time I worked
    for them.

    The towers were active so couldn't be earthed but had a
    lightning arrestor setup (effectively 2 spikes of metal with
    a small gap between them, the lower one deeply earthed,
    possibly being enough of an "earth" to draw in the lightning
    on the occasions it happened?) so that the charge could arc
    to earth if a strike did hit, and even with that arrestor a
    strike would still utterly destroy anything hooked into the
    tower. I'm guessing the arrestor was more to stop the bolt
    from flying down the cable and frying anyone in the shed
    where the equipment lived, basically taking the brunt of the
    power down to earth before it found a more lethal outlet.
     
    Hunter1, Jun 8, 2004
    #31
  12. Mick

    Unknown Guest

    Use all the words you want to make yourself appear as if you know what you
    are talking about - lightning jumps out of sockets through air into plugs
    when it decides it will go that way. Lightning burns out surge arrestors
    because they can not possibly stop it at all and it even burns out lightning
    arrestors meant to contain lightning when it feels like it. The fact that a
    surge protector survived means little when lightning is involved. It does
    what it WANTS to do, simple as that. Your safest bet is to have the plug out
    of the wall because there is less chance it WILL arc but it does it anyway
    when it feels like it. With the plugs in, you have a much better chance of
    getting toasted. Why? You are providing a direct path for it.
     
    Unknown, Jun 8, 2004
    #32
  13. Mick

    Unknown Guest

    Surge protectors aren't earthed. Ask any electrician who doesn't have a
    financial interest in selling the things and that person will tell you that
    they aren't worth a bone!
     
    Unknown, Jun 8, 2004
    #33
  14. Mick

    Hunter1 Guest


    I would guess that this would depend on the surge protector,
    any surge protector that's not earthed aint going to be
    worth a pinch of shit.

    As for them not being worth a bone, it all depends on the
    earth. The better the earth, the better the protection. It's
    all about providing the least prohibitive path to earth.
    That plugin box near my feet (with three prongs meaning it
    has an Earth which is near as good as the Earth in my power
    socket where it connects to) is only likely to offer very
    minor surge protection, aint going to help in a lightning
    strike but it'll probly sort Western Power doing something
    stupid like spitting out a spike. If I wanted to spend some
    money I could probably put in something much better that
    would have the whole house protected from surges and hooked
    directly into a real Earth, but the shit is so rare it's
    like playing Lotto. It might end up paying for itself but
    it's extremely fucking doubtful, and if the strike was
    direct to my power line out front even that wouldn't help
    matters except for maybe limiting the damage to equipment as
    opposed to those using said equipment.
     
    Hunter1, Jun 8, 2004
    #34
  15. Yep, all of those would be prime candidates, as all of them would actually
    be on with 'standby' power running through them, so they are already
    providing a path to whatever comes their way. I'd suspect the PC probably
    had either a phone line or some peripheral connected that was not isolated
    through that surge protector, thus providing a way around it.

    I've seen a very well protected PABX blown up (a few times) by having an
    old connected computer used for logging calls. The computer was not on
    the surge protector, and the hit blew it's serial port and the main board
    of the pabx. Lots of examples of that kind.

    However, note that I'm not suggesting that any surge protector will stop a
    direct lightning hit, but they considerably help to reduce the damage to
    equipment from lightning induced surges travelling down power and phone
    lines, and it's those that destroy most gear because they can travel a
    fair distance and destroy things over a much wider area. They are not
    'useless'.

    I do unplug the supply and phonelines to my important equipment overnight,
    and also my home gear when we go away for a couple of days or more.
    That's standard practice for Darwin residents. I disconnect from the
    upstream side of the surge protectors, so they are still clamping the
    lines to the equipment, and will help reduce induced voltages into cabling
    between the gear even if the building scores a direct hit.


    Noel Bachelor noelbachelorAT(From:_domain)
     
    Noel Bachelor, Jun 9, 2004
    #35

  16. So Lightning doesn't have to obey the laws of physics, because it can
    decide what it wants to do? Come on.


    Noel Bachelor noelbachelorAT(From:_domain)
     
    Noel Bachelor, Jun 9, 2004
    #36
  17. Mick

    Unknown Guest

    You haven't really seen what it can do, have you?
     
    Unknown, Jun 9, 2004
    #37
  18. Mick

    Hunter1 Guest


    Actually air is a quite viable path for lightning, it can
    quite happily leap even after hitting something and
    travelling down its' path if it finds a nice earth nearby
    (the lightning arrestors we used to use depended on that to
    sink most of the power hitting an active tower that we
    couldn't earth). That's what lightning does in the first
    place to get to earth. It doesn't require a copper
    connection to get to where it wants to go.
     
    Hunter1, Jun 9, 2004
    #38
  19. Mick

    Ken Taylor Guest

    You clearly believe that lightning is a living organism which will do what
    it wants, when it wants, rather than see it as a physical phenomena that we
    can work around. Consider this - Cape Canaveral is extremely
    lightning-prone, yet I know of only one incident which resulted in major
    damage (actually, that was a good-un - launched two Titan missiles!). Is it
    because they said "Oh, stuff it, lightning will do what it wants so let's
    not annoy it" or is it because they took proper (and no doubt expensive)
    precautions?

    Ken
     
    Ken Taylor, Jun 9, 2004
    #39
  20. Mick

    Unknown Guest

    You clearly don't know much about what lightning can do!
     
    Unknown, Jun 10, 2004
    #40
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