Leaving PC ON during lightning?

RichardH754 · 23 Jul 2013 at 05:44

Should we turn our PCs off and unplug them during a massive Thunder Storm?

dt97583 · 23 Jul 2013 at 07:28

What's all this we business

snips86x · 23 Jul 2013 at 07:33

I would if the storm was severe enough, but it passes to quick, I tend not to bother.

mattdunnapoo · 23 Jul 2013 at 10:03

kooobooom

na be fine unless its something from a sci fi movie

surge plug should hopefully stop it anyways ! well maybe ...

james_2k · 23 Jul 2013 at 10:09

ive lost a motherboard from a lightning strike. it came through the phone line into the pci modem.

but i still would turn my modern pc off just incase.

snips86x · 23 Jul 2013 at 10:14

Monitors have been struck too.

docsonic · 23 Jul 2013 at 10:31

Better safe than sorry I say! Why risk your investment for an hour or two's PC time..

d_brennen · 23 Jul 2013 at 10:36

Should you wear a hard hat at all times? Ya know, just in case a tile falls off a roof or a bock of blue ice from a 777 passing overhead

james_2k · 23 Jul 2013 at 10:39

d_brennen said:
Should you wear a hard hat at all times? Ya know, just in case a tile falls off a roof or a bock of blue ice from a 777 passing overhead

except lightning hitting your house, power line, phone line is not nearly as unlikely.

mad_weegie · 23 Jul 2013 at 11:52

the doc's alive he's in the old west

PiKe · 23 Jul 2013 at 11:56

When I worked in a computer shop for a short time we would always get people bringing their PCs in after thunderstorms saying they can no longer connect (dial-up) to the internet.

The PC wasn't struck per-se, it was more the voltage induced onto the telephone line from a nearby storm, this popped the 56k modem, the telephone lines were overhead in most cases to the property.

matthab · 23 Jul 2013 at 12:04

unplug it from the mains if its bad enough

DampDog · 23 Jul 2013 at 12:04

PiKe said:
When I worked in a computer shop for a short time we would always get people bringing their PCs in after thunderstorms saying they can no longer connect (dial-up) to the internet.

The PC wasn't struck per-se, it was more the voltage induced onto the telephone line from a nearby storm, this popped the 56k modem, the telephone lines were overhead in most cases to the property.

Yup had that happen. Quite a few years back now, there was a lightening strike but it was a couple of hundred yards away. Computer was fine but it killed the modem. And it frightened me to death, the flash & bang were simultaneous.

We have a mast-head amp for the TV mounted at the base of the ariel, so I tend to unplug that if storm is overhead. Not sure whether it sensible of not.

westom · 23 Jul 2013 at 14:30

PiKe said:
The PC wasn't struck per-se, it was more the voltage induced onto the telephone line from a nearby storm, this popped the 56k modem, the telephone lines were overhead in most cases to the property.

An induced voltage is so massive that it destroys every calculator, mobile phone, car radio, and wrist watch. Reality. That transient is so trivial as to be made irrelevant even by a less than 1 milliamp conducted by an NE-2 neon glow lamp. All those appliances contain protection that makes induced surges irrelevant.

We would trace damage to 56K modems. Damage is always a direct connection (a current path) from cloud to earth. Most often part damaged was the PNP transistor that drives a modem's off-hook relay. Creating a "No Dialtone Detected" message. Why did we know this. We traced every surge. And we fixed every damaged part. We used facts rather than speculation to know this stuff.

That transistor fails two different ways. Sometimes it fails shorted causing an off-hook relay to always remain closed. Then a modem will not hang up. Or it fails open meaning the modem's computer cannot connect to phone lines.

The most common source of that surge current is AC mains. A direct lightning strike far down the street is a direct strike incoming to every appliance. For example, incoming on AC mains through a computer's motherboard. Then out to earth via a phone line. Damage is often on the outgoing path; not an incoming path. Both current paths must always exist.

Well, lightning struck a lightning rod. Maybe 20,000 amps flowed to earth on a wire just outside and only a meter+ from an IBM PC. Did 20,000 amps of lightning adjacent to that PC cause damage? Of course not. An induced surge is a popular myth not based in reality. Due to protection routinely in every IBM PC and all other appliances, then that 20,000 amps caused nothing in the room to even blink.

Lightning damage is always a current into and out of an appliance. Often damage is on the outgoing side. Then wild speculation assumes that was the incoming path.

If a surge has an incoming path, then it always has another conductor for the outgoing path. Otherwise surge damage does not happen.

If that current was connected to earth BEFORE entering a building, then nobody need do anything to protect electronics. As proven by over 100 years of experience. And by every BT switching center.

Most never learn this. Instead, many want to install a magic box that somehow blocks that current. Nothing stops that current. Either it is connected to earth BEFORE entering. Or best protection is only what is already inside electronics.

PiKe · 23 Jul 2013 at 14:36

Well that's me well and truly educated.

snips86x · 23 Jul 2013 at 15:21

That's good to know.

Thanks!

VIPER258 · 23 Jul 2013 at 15:43

Interesting

amdhappy · 23 Jul 2013 at 16:40

I tried switching my PC on this morning after last night's electrical storm and not a sound or light came from it. Worked OK late yesterday evening, but this morning it is dead.

Plugged into surge protector, so that obviously didn't help.

Going to try again after work today, but I sense the PSU is gone. Hopefully that is all.

w.

RHS · 24 Jul 2013 at 00:42

So basically your PC is probably safe enough but if in doubt plug it out

westom · 24 Jul 2013 at 02:30

RHS said:
So basically your PC is probably safe enough but if in doubt plug it out

Multiple AC wires enter. Do all connect to earth? If yes, then a surge has a shorter and less destructive path to earth. However not all AC wires can connect direct to earth.

Those other wires only make a low impedance earth connection IF connected via a 'whole house' protector. Only one wire can connect directly (hardwired). All other AC wires must be earthed via a 'whole house' protector. Otherwise that is a path for a surge current to enter the building. To go hunting for earth destructively via appliances.

A 'whole house' protector is a completely different device from adjacent protectors. These two completely different devices unfortunately share a common name. The protector that connects a surge current harmlessly to earth must have a dedicated wire for that low impedance ('less than 3 meter') connection to earth. Earth is not the safety ground prong on a wall receptacle. Earth ground is an electrode in earth.

BT wires cannot connect directly to earth. So again, a protector must connect each and every wire to the same earth ground. Otherwise any one wire can be carrying a destructive transient into household appliances.