# Is it safe to use computer during lightning/thunder storm?

N

#### nospam256K

Jan 1, 1970
0
Here in New York City (Manhattan) where I live, I usually use a laptop
computer running on an AC adapter, and get online via a dial-up modem
(phone line plugged into computer's built-in modem).

When it's merely raining outside, it's usually of no concern to me.
But when there's lightning or thunder, I quickly get offline, turn off
the computer, and literally unplug the AC adapter from the outlet, and
unplug the phone line from the computer.

This is done to avoid the possibility of the AC adapter or the modem
suffering damage from a voltage spike carried through either the AC
power line or the phone line (because of a lightning strike).

Does all this sound sensible to you, or am I being
overly/unneccesarily cautious?

R

#### Ron Reaugh

Jan 1, 1970
0
nospam256K said:
Here in New York City (Manhattan) where I live, I usually use a laptop
computer running on an AC adapter, and get online via a dial-up modem
(phone line plugged into computer's built-in modem).

When it's merely raining outside, it's usually of no concern to me.
But when there's lightning or thunder, I quickly get offline, turn off
the computer, and literally unplug the AC adapter from the outlet, and
unplug the phone line from the computer.

Not dumb.
This is done to avoid the possibility of the AC adapter or the modem
suffering damage from a voltage spike carried through either the AC
power line or the phone line (because of a lightning strike).

Does all this sound sensible to you, or am I being
overly/unneccesarily cautious?

I always do it too.

J

#### John Popelish

Jan 1, 1970
0
nospam256K said:
Here in New York City (Manhattan) where I live, I usually use a laptop
computer running on an AC adapter, and get online via a dial-up modem
(phone line plugged into computer's built-in modem).

When it's merely raining outside, it's usually of no concern to me.
But when there's lightning or thunder, I quickly get offline, turn off
the computer, and literally unplug the AC adapter from the outlet, and
unplug the phone line from the computer.

This is done to avoid the possibility of the AC adapter or the modem
suffering damage from a voltage spike carried through either the AC
power line or the phone line (because of a lightning strike).

Does all this sound sensible to you, or am I being
overly/unneccesarily cautious?

Your precautions are very sensible. Not only is the computer, modem
and power supply at risk, if you happen to be near a ground
connection, your body is at some risk, also.

However, there is a simple precaution you can take that makes it much
safer to use your computer during a rain storm. Get a filtered, surge
suppressed power strip that has both receptacles and phone line
sockets. The surge suppressers help limit the voltage peaks between
any of the incoming power lines, which protects the supply, but also
limits the peak voltage between the phone lines and the power ground,
protecting both the modem and you from anything but a very close
strike. I still wouldn't use it in the bath tub, though.

Here is an example of one without a low pass filter (just surge
suppressers):
http://www.connectxpress.com/product.asp?cat_id=4301&sku=29799
And a bigger unit that includes the RFI filter (that improves the
operation of the surge suppression a bit).
http://www.connectxpress.com/product.asp?cat_id=4301&sku=29798

I am not endorsing these particular products, just using them as
examples of what I am talking about.

O

#### Odd Bob

Jan 1, 1970
0
Here in New York City (Manhattan) where I live, I usually use a laptop
computer running on an AC adapter, and get online via a dial-up modem
(phone line plugged into computer's built-in modem).

When it's merely raining outside, it's usually of no concern to me.
But when there's lightning or thunder, I quickly get offline, turn off
the computer, and literally unplug the AC adapter from the outlet, and
unplug the phone line from the computer.

Very wise. A couple years back I had a modem fried by a nearby
lightning strike and I'm grateful that's all that was fried. These days
if I even think I hear thunder I pull all the plugs and go read a good
book. My suggestion, anyway...

-- Bob

S

#### Sporkman

Jan 1, 1970
0
The greatest danger is from your modem. Surges coming in through
telephone lines can do quite a bit of damage. In fact, I've had
desktops almost completely smoked via the modem. Fried the motherboard,
video, AND drives (both CD and HDD). Spared the RAM and the power
supply and not much else. And yes, it is absolutely certain that it was
through the telephone line, not through the power line. Surge
suppressors and uninterruptible power supplies MAY protect from
telephone line surges well enough, or they may not. After having a
computer smoked and having seen my neighbor's computer smoked in the
same way I stopped using internal modems altogether, but of course
external modems are seldom used with a laptop. Your computer power
supply will possibly protect your laptop well enough from power surges
with sacrificial diodes in the rectifier circuit, but it's a better bet
to unplug and run off the battery. I'm sure you don't want to even have
to buy a new AC supply for your laptop. Those can be expensive,
although Radio Shack carries AC supplies that MAY be enough for your
computer (mine actually requires more amperage than the RS model can
supply on startup, and if the battery is down the thing won't boot).

Mark 'Sporky' Stapleton
Watermark Design, LLC
www.h2omarkdesign.com

B

#### Bigbazza

Jan 1, 1970
0
Sporkman said:
The greatest danger is from your modem. Surges coming in through
telephone lines can do quite a bit of damage. In fact, I've had
desktops almost completely smoked via the modem. Fried the motherboard,
video, AND drives (both CD and HDD). Spared the RAM and the power
supply and not much else. And yes, it is absolutely certain that it was
through the telephone line, not through the power line. Surge
suppressors and uninterruptible power supplies MAY protect from
telephone line surges well enough, or they may not. After having a
computer smoked and having seen my neighbor's computer smoked in the
same way I stopped using internal modems altogether, but of course
external modems are seldom used with a laptop. Your computer power
supply will possibly protect your laptop well enough from power surges
with sacrificial diodes in the rectifier circuit, but it's a better bet
to unplug and run off the battery. I'm sure you don't want to even have
to buy a new AC supply for your laptop. Those can be expensive,
although Radio Shack carries AC supplies that MAY be enough for your
computer (mine actually requires more amperage than the RS model can
supply on startup, and if the battery is down the thing won't boot).

Mark 'Sporky' Stapleton
Watermark Design, LLC
www.h2omarkdesign.com

used..But cable is !...So do I need to turn my Cable Modem off as well ..or
not..?..

Bigbazza

T

#### Todd Copeland

Jan 1, 1970
0
Bigbazza said:
used..But cable is !...So do I need to turn my Cable Modem off as well ...or
not..?..

Turning it off would help. but _very_ little. Unplugging it would be the
correct thing to do. I"ve had more analog modems fried by lightning (4) then
cable modems (2) but you can see, it happens. Personally I don't bother with
unplugging the cable modem as Brighthouse really does not have a problem
replaceing them with no charge.

R

#### Roger Johansson

Jan 1, 1970
0
Bigbazza said:
used..But cable is !...So do I need to turn my Cable Modem off as well
..or not..?..

If you live in a densely populated city and all these cables come through
underground cables there is very little risk for damage from lightning.

The high voltages from a lightning must then travel long distances
through underground cable systems, and the power is distributed among
thousands of end users connections.

There is probably also good protection systems in place to protect
against overvoltage conditions.

Earlier I lived in a small old house on top of a mountain, with
electricity and phone lines coming through the air, wires on poles.

Now that was a risky place to live at during lightning storms!

And there was often lightning hits even on clear days,
without any warning signals in the weather at all.

I have had my telephone practically explode a few feet from my head, and
I have had lots of equipment destroyed.
Mainly modems and tv sets but also other stuff.

Then I installed some protection components, spark gap devices, on both
the electricity and phone lines. Where the lines enter the house and
inside the house, close to the computer and tv set too. I also increased
the lightning protection for the house with lightning rods and lots of
wires in the ground around the house to absorb the power better.

That helped a lot, and I had no equipment destroyed for those 6 years
I lived there when I had the protection components installed.

Compared to my house on a mountain you are very well protected in a
densely populated city with underground cable systems for electricity,
phone lines, cable tv and cable internet.

A lot of people have a situation somewhere between these two extremes,
big city or mountain top, and may want to take necessary precautions.

The easiest way to add protection to vital equipment is to put all of it
on an extension cord with multiple outlets and add protection circuits to
that extension cord system. Make sure that both phone connection and
electricity connection are protected where they enter that extension cord
system.

C

#### Code Developer

Jan 1, 1970
0
Does all this sound sensible to you, or am I being
overly/unneccesarily cautious?

No, very sensible!

About a year ago, we had a thunder storm where a bolt of lightening actually
struck our back garden. The PC in the office was protected by a UPS /
filter, but the DSL connection through the phone line and the external
modem/router weren't protected. The lightening fried the modem and the
network card in the PC! Fortunately the rest of the PC was ok.

Now, the PC is protected by a UPS, and the modem/router's phone connection
is filtered through a surge protection device.

Regards,
Shaun.

A

#### Alex Rodriguez

Jan 1, 1970
0
Here in New York City (Manhattan) where I live, I usually use a laptop
computer running on an AC adapter, and get online via a dial-up modem
(phone line plugged into computer's built-in modem).
When it's merely raining outside, it's usually of no concern to me.
But when there's lightning or thunder, I quickly get offline, turn off
the computer, and literally unplug the AC adapter from the outlet, and
unplug the phone line from the computer.
This is done to avoid the possibility of the AC adapter or the modem
suffering damage from a voltage spike carried through either the AC
power line or the phone line (because of a lightning strike).
Does all this sound sensible to you, or am I being
overly/unneccesarily cautious?

Sounds sensible to me. You could also try getting a good surge protector.
Then you won't have to unplug everything. I would make sure that the phone
cable also runs through the surge protector or unplug it.

D

Jan 1, 1970
0
There are 3 potential failures here:
o Data-corruption from power failure
---- for a laptop this risk is removed (usefully
o Modem is damaged thro telco system
---- not impossible even in NYC, not uncommon in rural or elsewhere
---- for an onboard modem you 1) lose your modem or 2) lose the laptop
---- both of which involve downtime & expense
o Computer is damaged through mains system
---- lightning will happily hit buildings, then run thro mains systems

It's not uncommon for lightning some distance away to cause line-drops,
as well as major power dips (brownouts/sags) and surges. Computer PSU
are switched-mode PSUs so tolerant of large variations in power, but that
is not a guarantee where lightning is concerned.

Telephone cables often run outside a building, along walls, which can be
interesting re picking up voltage from lightning or attraction.

When lightning appears to have gone, remember it can still strike some
distance from the originating storm - even in blue-sky. That is how most
people are struck by lightning, and potentially buildings, power poles etc.

If your power comes in thro a pole transformer, and same for telco, then
local lightning can pose a serious risk to both power & telephone services.
Colleague lost the corner of their tiny sub-let warehouse last year due to
a lightning strike - what wasn't burnt was electrically damaged.

So whilst it may seem old-fashiooned, it's not a bad idea.
Certainly unplugging the telco connection. In the UK the master telco socket
has a GDT, gas discharge tube, but if lightning is close they're a bit useless.
If something nearby is hit, the surge protectors can save a modem etc,
but a direct or very close strike will generally take out anything re energy.

W

#### w_tom

Jan 1, 1970
0
A wide variety of good responses and outright myths. Some
just post answers without even providing a single reasons
why. Those posters are particularly insidious and typically
respond with insults.

Turning something off will not help. Destructive surges
were not stopped or absorbed by 3 miles of air. Why then will
millimeters inside a switch do what miles of air could not?

In the early days of ham radio, equipment would suffer
lightning damage. Antenna lead was disconnected and even put
inside a mason jar. Damage finally stopped when the antenna
lead was connected to earth ground. They only rediscovered
what Ben Franklin demonstrated in 1752. Lightning seeks earth
ground. If not earthed before entering a building, then
lightning will seek earth ground, destructively through
appliances.

Some will claim that a plug-in protector would help. Again,
plug-in protector will stop or block what miles of air could
not? So very quietly, those plug-in manufacturers forget to
mention they don't even claim to protect from that destructive
type of surge. Obviously. No dedicated earth ground. They
just let others assume all surges are the same type.

Industry professionals demonstrate how protection is
installed as it was proven before WWII on the Empire State
Building.

http://www.erico.com/public/library/fep/technotes/tncr002.pdf
Two structures each with their own single point earth ground.
Any wire entering each structure first makes a connection to
that earth ground. Connection either by a hardwire or via a
surge protector. Notice what an effective surge protector
does. Makes a temporary and short connection to earth ground
during a surge.

Also notice the buried phone wire in that figure. Even
underground wires must first connect to that single point
earth ground. Yes even underground wires will carry
destructive surges inside a building.

So what can you do? Protection is a building wide
solution. However if your circuit breaker box is 'earthed'
(connected) to building steel, then it already has an
excellent single point ground. Breaker box then gets a 'whole
house' protector so that surges entering on AC mains are
immediately earthed long before they can get to your
computer. Most destructive surges - especially to modems and
portable phone base stations - are incoming on AC electric.

Same applies to phone line. But phone line already has an
effective protector provided free by the telco because 'whole
house' protectors are so effective and so inexpensive. Cable
company is also required to bond to earth ground where cable
enters the building. Cable requires no surge protector
because cable can make a direct (hardwired) connection to
earth ground.

All electronics contains internal protection. Anything that
is effective on an appliance power cord would already be
inside the appliance. But that internal protection assumes
destructive transients are earthed before entering a
building. Earthed transients will not overwhelm protection
already installed in appliances. Again, protection that has
been proven repeated in virtually every town for so many
decades. Protection that does not use plug-in protectors.

Do not fall for urban myths that a UPS or power strip will
filter or stop surges. Again, a 1 inch component will stop
what miles of sky could not? Of course not. A UPS will stop
or filter a surge? Franklin did not stop or absorb
lightning. He shunted (diverted, connected) an electrical
transient to earth so that it did not seek earth ground via a
church steeple. Effective protection inside telephone
switching centers, 911 emergency response centers, and even in
grocery stores do same.

A telephone switching center connected to overhead wires
everywhere in town does not unplug during thunderstorms. And
yet that is what your are being told. They simply connect
every incoming wire to single point earth ground where wires
enter the building. Protection that is best located 50 meters
from computers.

The plug-in protector does not even claim to protect from
the destructive type of surge. It claims to protect from
surges that don't typically exist. Myth purveyors then assume
protector protects from all kinds of surges - not knowing that
different types of surges exist.

Plug-in manufacturer encourages others to play word games as
if it was technical fact. Surge protector and surge
protection are same? No. All protection 'systems' require
surge protection - earth ground. Only some incoming utilities
require a surge protector to connect to surge protection. A
surge protector is only as effective as its earth ground.
Plug-in protector manufacturers even avoid discussing earth
ground. Telling the 'whole truth' would only hurt profits.
Effective protection is a 'whole house' protector. Therefore
internal appliance protection will not be overwhelmed. A
surge protector is only as effective as its earth ground.

Recommended is a 'whole house' protector at AC mains
electric box. That is effective protection for about $1 per protected appliance. R #### Roger Johansson Jan 1, 1970 0 w_tom said: Some will claim that a plug-in protector would help. Again, plug-in protector will stop or block what miles of air could not? So very quietly, those plug-in manufacturers forget to mention they don't even claim to protect from that destructive type of surge. Obviously. No dedicated earth ground. They just let others assume all surges are the same type. A good surge protector contains one or more of these components: A spark gap device, also called ComGap, which allows overvoltage, charge, to jump to the earth connection. A VDR which is slower than the Comgap, but it lowers the voltage to zero, which protects the Comgap, this is needed if we are talking about a mains wire, because mains delivers current until the mains cycle reaches the zero crossing, and this current hurts the Comgap device. A Comgap needs to be used in series with a resistor, a big mass type resistor, value 20 Ohm or so. The VDR is used in parallell with this Comgap-resistor combination. To make the protection better one can use small coils in the signal/mains way, after the comgap. The coils stop fast voltage changes and make the comgaps take the charge instead. The comgaps and the VDR:s need to have the right voltage, 450Volt for a 240Volt mains wire, a 140Volt for the phone line. It doesn't hurt the computer and other devices if the voltage is raised a thousand volts for a short moment, as long as all connections to it are raised together. So the surge protector only has to keep all connections at fairly the same voltage, even if they all are raised momentarily. What really hurts the equipment is if one of the connections moves far away from the other connections, because then there is a surge inside that piece of equipment, burning some component to pieces. That is why the extension with outlets protected by a surge protector works. It creates a subsystem which is kept together at virtually the same potential for all connections to that subsystem. When a modem is hurt by the lightning it is because the mains connection to it and the phone connection to it are pulled apart by thousands of volts, and that creates a damaging surge inside the modem. If both the mains and phone line connections to the modem first have to pass through a protector box, where they are prevented from moving apart too much, voltage-wise, the modem is protected. W #### w_tom Jan 1, 1970 0 An adjacent surge protector contains a device that does not stop surges. It simply shunts all wires together during that surge. A surge shunted from one wire to all others goes where? Remember, the destructive surge seeks earth ground. It now has more paths to find earth ground, destructively, via the adjacent computer. What kind of protection is that adjacent protector? Ineffective. Telcos prefer their protectors located 50 meters from a$multimillion switching computer. Protectors adjacent to the
computer might only shunt the surge to earth through that
restrictions to how cable is installed. Connection from cable
to earth ground must be significantly shorter than connection
from same point to TV or cable modem. Why? Effective
protector is distant from transistor and adjacent to earth
ground.

A surge protector is only as effective as its earth ground.
Effective protectors make a 'less than 10 foot' connection to
earth. No plug-in protector will make that connection. Just
another reason why plug-in protectors are so ineffective.
Just another reason why plug-in protector manufacturers avoid
all discussion about earthing. They don't claim to protect
from that type of surge.

destructive surges are normal mode. Destructive surges are
longitudinal mode. That means a surge shunted by the power
strip will seek many paths back to earth ground - including
destructively through a computer modem. The resulting error
message may be 'No Dialtone Detected'.

Damage you demonstrate inside a modem is classic of a surge
that enters on AC electric. Remember primary school science.
First electricity must flow through everything in that
circuit. Only later does something fail. A complete circuit
from cloud to earth is fully energized. Then the modem
fails. Classic modem damage is a surge that enters on AC
electric, passes through modem, then outgoing to earth ground
on phone line. This surge often damages the modem's DAA
section - the phone wire side of modem.

Many assume surges act like ocean waves. The surge destroys
the first component encountered? Of course not. Surge first
travels through everything in the circuit. Only then does
something fail. A failed DAA section does not say where surge
comes from. But many will tell us the surge ignored a telco
installed 'whole house' protector to enter modem via that
phone line. Why does surge completely ignore the phone line
'whole house' protector? Because many don't even know the
protector exists.

Surge enters on utility wire that has no 'whole house'
protector - AC electric. It then leaves (makes a complete
electrical circuit) by leaving - going to earth ground - via
phone line.

How does the phone line surge completely ignore a telephone
company installed 'whole house' protector? It must to enter
on phone line.

Your theory is good IF surge is normal mode.
Manufacturer's specifications claim to protect from normal
mode transients. Problem is that destructive surges are not
normal mode. So manufacturer forgets to mention two things:
1) plug-in protectors don't provide protection from the
typically destructive type of surge and 2) earth ground. By
forgetting to mention other types of surges, they have
promoted protection myths. Many then *assume* it protects
from all types of surges.

Destructive surges must be earthed before entering a
building. Then protection internal to all household
appliances will not be overwhelmed.

Let's see. We spend $15 or$50 to protect only one
appliance. What protects smoke detectors, intercom,
dishwasher, etc? Effective 'whole house' protector costs
about $1 per protected appliance. Furthermore it provides protection from all types of surges. Plug-in protectors don't make such claims. Your example only demonstrate that plug-in protectors work as speced. Your example forgets to discuss the type of surge that typically damages electronics. All appliances contain any protection that is effective adjacent to appliance. Internal protection that requires 'whole house' protection on every utility wire where that wire enters building. Why are plug-in protectors often so undersized - have so few joules? They are not really selling effective protection. Why waste good money on more parts - more joules? Profit - not protection - is the agenda with plug-in protectors. Those who know surge protection do not speak of Tripplite, Panamax, Belkin, or APC. They discuss a benchmark in surge protection - Polyphaser. Polyphaser application notes are legendary. Polyphaser makes a protector that has no connection to earth ground. Distance to earth ground is so critical that the Polyphaser protector sits directly ON earth ground. That is zero feet to earth ground. Distance to earth ground is that critical to effective protection. No earth ground means no effective protection. So plug-in manufacturers avoid the whole earthing topic all together to sell their ineffective products. A surge protector is only as effective as its earth ground. S #### Shawn Hearn Jan 1, 1970 0 Here in New York City (Manhattan) where I live, I usually use a laptop computer running on an AC adapter, and get online via a dial-up modem (phone line plugged into computer's built-in modem). When it's merely raining outside, it's usually of no concern to me. But when there's lightning or thunder, I quickly get offline, turn off the computer, and literally unplug the AC adapter from the outlet, and unplug the phone line from the computer. This is done to avoid the possibility of the AC adapter or the modem suffering damage from a voltage spike carried through either the AC power line or the phone line (because of a lightning strike). Does all this sound sensible to you, or am I being overly/unneccesarily cautious? The odds of a lightning strike doing any damage in a densely populated region such as Manhattan are astronomically slim. If I lived in that area I wouldn't worry about it. There are so many tall buildings in Manhattan to attract lightning and the majority of them probably have lightning rods on them. The situation in a rural area is different. I once had some electronic equipment fried by a nearby lightning strike a few years ago in a suburban Philadelphia home. S #### Shawn Hearn Jan 1, 1970 0 Roger Johansson said: A good surge protector contains one or more of these components: The average person does not have a "good surge protector." R #### Roger Johansson Jan 1, 1970 0 w_tom said: Your example of an adjacent power strip protector works IF destructive surges are normal mode. Destructive surges are longitudinal mode. That means a surge shunted by the power strip will seek many paths back to earth ground - Damage you demonstrate inside a modem is classic of a surge that enters on AC electric. Remember primary school science. First electricity must flow through everything in that circuit. Only later does something fail. protection - Polyphaser. Polyphaser application notes are legendary. Polyphaser makes a protector that has no connection to earth ground. Distance to earth ground is so critical that the Polyphaser protector sits directly ON earth ground. That is zero feet to earth ground. I feel like I am discussing loudspeaker cables with an audio hi fidelity enthusiast. You obviously do not understand what I am saying, but you have a lot to say about special modes, earth connections and special brands, which doesn't make sense from a scientific point of view. You do not have an education in electronics, but you have a brain filled with blurb from advertisements. W #### w_tom Jan 1, 1970 0 If you don't understand normal and longitudinal mode, then you do not even have first year engineering knowledge. People with insufficient knowledge that can promote myths about plug-in protectors. If you think that power strip surge protector provides more than normal mode protection, then simply cite the manufacturer's spec. I state this knowing full well there is no such spec. Manufacturer does not even claim to provide that protection. Why then would you? You are confusing normal mode with longitudinal mode. Lets put numbers to your previous example. Lets say a small (100 amp) transient approaches your power strip surge protector. Let's say the wall receptacle connects to breaker box with 50 feet of 12 AWG wire inside walls. Now let's assume your power strip protector shunts all 100 amps to wall receptacle safety ground. That 50 foot wire is less than 0.2 ohms resistance. But to the transient, it is something on the order of 130 ohms impedance. Basic engineering. Wire has impedance. 100 amps times 130 ohms puts the power strip protector at something less than 13,000 volts. Will that 13,000 volts try to obtain earth ground via 50' safety ground wire? Of course not. It will seek many other paths to earth ground. One destructive path is via computer modem and telephone wire. So what has that power strip surge protector done? Again, nothing complex here. The concepts only require first year engineering. That power strip has shunted the 100 amp surge from black hot wire onto all other wires. It has contributed to damage of an adjacent and powered off computer. I don't understand why you have so much difficulty with the concept; assuming you have engineering training. These numbers only demonstrate what has been well understood for generations. Surge protection has always been about earthing a surge before it can enter a building. Need I again cite how telephone switching centers are constructed so as to not suffer surge damage. Need I again cite the legendary application notes of Polyphaser? What advertisement? Anyone familiar with real surge protector knows this name as an industry benchmark: http://www.polyphaser.com/ppc_technical.asp Or maybe the National Institute of Science and Technology might help. They are not advertising. Their figure is used to demonstrate how a fax machine is protected or may be damaged. Again 'whole house' protector and the all so critical single point earth ground: http://www.epri-peac.com/tutorials/sol01tut.html Yes, you made a good case for normal mode protection. But that is not the type of surge that typically damages electronics. How many industry professional citations need I provide? A surge protector is only as effective as its earth ground. A fact well proven even before WWII. R #### Rich Grise Jan 1, 1970 0 Here in New York City (Manhattan) where I live, I usually use a laptop computer running on an AC adapter, and get online via a dial-up modem (phone line plugged into computer's built-in modem). When it's merely raining outside, it's usually of no concern to me. But when there's lightning or thunder, I quickly get offline, turn off the computer, and literally unplug the AC adapter from the outlet, and unplug the phone line from the computer. This is done to avoid the possibility of the AC adapter or the modem suffering damage from a voltage spike carried through either the AC power line or the phone line (because of a lightning strike). Does all this sound sensible to you, or am I being overly/unneccesarily cautious? An apartment I was living in once took a direct hit. It's pure dumb luck that I had unplugged the modem - it took out the answering machine and a desk phone. It also blew out a couple of exit lights - the manager said there was a total of about$7,000 damage from that one
strike.

So, if it's actively lightninging, you're not being overly/unneccesarily
cautious to unplug stuff. It also took out the on/off transistor in
the TV, so the remote wouldn't turn it off any more. I had to get up
and walk to the TV, until I got it fixed, of course. I took it to
the shop, and asked how much a diagnosis was, which was about $35.00, and the repair would have been about$85.00, so I just asked the tech
to mark the transistor so I could replace it myself. I had to rearrange
the leads on a plastic 2222, but it fixed it.

Cheers!
RIch

R

#### Roger Johansson

Jan 1, 1970
0
w_tom said:
http://www.polyphaser.com/ppc_technical.asp

Or maybe the National Institute of Science and Technology
might help. They are not advertising. Their figure is used
to demonstrate how a fax machine is protected or may be
damaged. Again 'whole house' protector and the all so
critical single point earth ground:
http://www.epri-peac.com/tutorials/sol01tut.html

A lot of useful information in these links, but you still need an
education in electronics to fully understand that information.

Like Henri Poincare said: Facts are just the building blocks of science,
you need to know how to build them together, you need models and
theories, that is real science.
Yes, you made a good case for normal mode protection. But
that is not the type of surge that typically damages
electronics. How many industry professional citations need I
provide? A surge protector is only as effective as its earth
ground. A fact well proven even before WWII.

"Ground Potential Rise (GPR)", is used a lot on the Polyphaser web site.
If you understood what it means you would not write about "sitting ON
earth", as you did in your earlier message, because no point can be
exactly "on earth" during a thunder storm. All points are moving
voltage-wise, so you have to choose a suitable moving point and use it in
a proper way.

As I stated earlier, the important thing is not to keep everything
the important thing is to prevent different parts of the system from
moving too far apart voltage-wise.
And that is what we use spark gaps and other devices for.
This can be done for a whole building or for subsystems within a building.

M
Replies
2
Views
693
Lord Garth
L
Replies
3
Views
441
Replies
3
Views
483
Replies
1
Views
1K
Replies
3
Views
940