Marty Michener wrote:
>
> At 04:39 PM 7/10/02 -0400, Walt wrote:
> >My theory is that the power surge that came in was riding on only one
> >leg of the power. And the SCSI card got caught in the middle and that
> >was how it all got into my computer. Also caught in the middle was the
> >ethernet lan. My computer lost the transmit side of it's ethernet, the
> >others lost the receive. It's not clear if the phone line surge was
> >internal to the house from this difference, or a separate surge that
> >came in from outside via the phone line. It's only damage was fried
> >suppressers.
>
> Walt - what a terrible time you have been having - my hopes for speedy
> resolution go out to you and the troubled lan. It makes you wonder when
> you read about Electro-Magnetic Pulse terrorism, if it ain't already here. ;=D
The difference being there's no people I can go hunt down. It's all just
part of living.
Right now it primarily is a problem printing, and each of us must use a
modem separately to connect to the internet one at a time. (I'm typing
this on my G4 with it's damaged motherboard.) We previously routed a
single modem through my machine via the lan so that all could be on
simultaneously. It's going to be more tricky as each motherboard has to
be sent in for repairs. I may be able to arrange a exchange with the
repairer which would mean no down time to speak of. We are fully capable
of handling the boards and so on but don't have enough info for
component level repairs, especially as no damage is showing. I even have
a copy of apple's official service data and testing software. (another
goodie from ebay) But they just do board exchange.
> Of course they tell you lightening travels from the ground up into the sky,
> not the reverse the way is popularly assumed. I'm not sure there even IS a
> difference, here, but ok. ;^)
I don't think it matters. Certainly the diodes in computer equipment are
way too weak to stop it either way. I know it's a upward current, but
still persist in talking like it's down. Probably got to that as a
child. It's more satisfying to blame the storm for hitting you than to
say the earth got you while shooting at the storm.
> So I have come to look, in cases of near bolts, for indications of ground
> potential itself having been shifted radically. And this is the way I
> would surmise your two-leg problem. The problem with saying the bolt came
> in primarily on one leg is that lightening energy is so rapid it will
> hardly go around any corners, like ordinary house wiring, because of the
> high inductive impedance at that high a frequency of a simple "U" in the
> wire. I think we need those ferrite anti-rf blocks around all wire and
> cable leads entering our domains. You can assume the "ground" itself moved
> toward one leg and away from the other leg, or that the two ground
> locations became momentarily separated by many, many volts. I also suggest
> that the surge that killed the lan was induced, rather than conducted, but
> this would be hard to do physically if it is either twisted pair or coax.
The lan is all cat5 twisted pair, RJ45 ends. And it's in the crawl space
but not laying on the ground. The bolt was more than a half mile away.
The entire storm and the bolt involved never came near the house.
Whatever we got I assume was through the phone or power lines.
I think my explanation is simplistic, but suitable for the question of
what to do for next time. What I'm doing amounts to making sure both
ground and power are same leg. And adding another layer of surge
suppressers in the lines connecting everything to try and isolate each
computer from the others.
This is in tune with my previous experiences. I've not had a direct
power line surge problem. My first loss was clearly induced voltage in
the line high in the house. The second one had a clear path of
destruction that began from the phone line and was conducted through the
lan via my motherboard. (or the reverse if we are to take note that it
ended in the sky)
Your idea of the Ferrite anti-rf blocks is interesting. It's cheap, so I
may try it on the phone lines, which seem to be my main problem. The
phone line is underground for the last 200' to the house. That was done
a few years ago when the overhead line went bad.
Our well, and the entrance line for the power both have the spark gap
type protection which is connected to the well casing and a ground rod
respectively. Before we bought the house it lost two well pumps in
succession before that was put on.
> I am afraid I have more questions than suggestions, but, really, Walt, as
> in all things, I do marvel at your patience.
I've a lot of questions too, but most importantly I have a plan built
from what I know. The test of the value of the plan will be how long
before the next time I have damage.
My parents have a old movie of a argument between my sister and I. Or
more like she was mad at me for some reason which I've long forgotten,
heck other than the movie I can't remember the incident. The movie shows
my older sister dragging my trike down into a ditch. And me patiently
dragging it back out. And my sister even more enraged running, grabbing
it from me and dragging it back and throwing it into the ditch. And me
patiently dragging it back. This goes on until my sister got so enraged
she could only lay on the ground screaming a tantrum as I ride my trike
away. I was 4 or 5 at the time. According to my mom, who took the movie,
this unfolded over several hours one afternoon. I go way back on
patiently fixing problems. It works.
Walt
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