Re: Modem problem
- From: w_tom <w_tom1@xxxxxxx>
- Date: Fri, 31 Aug 2007 09:35:44 -0700
Appreciate why lightning may have found a path to earth via your
modem. First some facts that you may not know and that Paul clearly
does not know. The telephone line already has a superior protector
installed for free by the telco. An effective protector if your
earthing is sufficient; if you provided that telco installed protector
a better earth ground.
So how was a modem damaged - internal or external? Remember, we are
discussing electricity. That means a path into and out of everything
in that circuit must exist. That means surge currents are flowing
through everything in that path long before anything is damaged.
Wires highest on utility pole are most often struck - AC electric.
A lightning strike down the street to AC wires is a direct connection
to your modem - just like an antenna to a radio. Lightning seeks
earth ground. Incoming on AC electric, through your computer
motherboard, through modem, then out to earth ground via that telco
installed protector.
Lightning would not enter on phone line. Why would a surge seek
earth ground via phone line when telco protector has already connected
lightning to earth? Most common incoming path for surges seeking
earth ground is AC electric.
Paul has assumed a protector will somehow stop or absorb what three
miles of sky could not. He has assumed protectors are some kind of
'magic box' protecting device. He then cited products from a
manufacturer who does not have a reputable name but that is hyped in
industry myths. Where does that protector discuss earthing? It does
not because it does not even claim to protect from that type of
surge. Don't take why word for it. Review its numeric
specifications. Where does it cite each type of surge and protection
from that surge? It does not. Is it a complete 'magic box'
protection. Why does it not make that claim in specs?
Effective protector earths before a surge can enter a building.
Notice the telco has already installed one for free. Free? Yes
because it is so inexpensive and so effective. Cable TV needs no
protector. Their cable is earthed using only a wire - even better
protection. In every case, what provides protection? Single point
earth ground. Protector is simply an connecting device to protection.
Protector is not protection. Cable and telco installed protector both
must be earthed to the same grounding electrode. Same solution also
applies to AC electric.
Three wires are inside the AC cable. One is connected directly to
earth (if your home meets 1990 NEC requirements). Other two wires
have no earthing connection. Manufacturers with responsible names -
Square D, Leviton, Intermatic, Cutler-Hammer, Siemens, GE, etc - make
a 'whole house' protector with that dedicated earthing wire. Again,
where is the earthing wire on those Tripplite protectors? Oh?
Tripplite 'magic box' needs no earthing wire because it will magically
stop what three miles of sky could not?
Instead we install one 'whole house' protector so that AC electric
is earthed to same electrode used by cable TV and telephone. AND we
upgrade earthing to both meet and exceed post 1990 code so that that
connection from protector to earth ground is 'less than 10 feet', no
sharp bends, no splices, earthing wire is separated from all other non-
ground wires, etc. Water pipe earth ground is typically no longer
sufficient both in code AND for better surge protection.
Paul may claim that Tripplite is grounded by wall receptacle safety
ground. Some UPSes would do same ineffective protection. UPS and
Tripplite grounding violates every one of those earthing
requirements. Ground wire far exceeds 10 feet. It is spliced
repeatedly. It is bundled with other non-ground wires. It has too
many sharp bends to count. IOW the Tripplite has no earthing. And
yet somehow it will earth destructive surges? Of course not. Instead
Tripplite lets their 'magic box' stop what three miles of sky could
not. Actually Tripplite does not make that claim. They just let
others promote those myths for them.
Protection means earthing where surges would enter the building. A
surge protector is only as effective as its earth ground. The most
likely source of a modem destructive surge - follow a path into and
out of that modem. Incoming on AC electric. Outgoing via telephone
wire.
One final point. This modem damage can be repaired. A path from AC
electric to phone line typically is via modem off hook relay.
Incoming via PNP transistor that drives that relay. Outgoing via
relay wiper (switch) to phone line. That PNP transistor is most often
damaged. Everything else is still OK. Replace that transistor and
the modem may work for years. Surge damage because AC electric box
did not earth the incoming surge via a 'less than10 foot' connection.
Protector is only as effective as its earth ground. "Magic box'
solutons hope you never learn that. No earth ground (ie Tripplite)
means no effective protection.
On Aug 30, 1:45 pm, Ken Knecht <kenk6...@xxxxxxxxx> wrote:
My built-in modem quit working this morning. Running XP Home. It was
raining, my UPS came on for a few moments and I heard a sharp bang
outside. The internal modem then went off line. When I tried to get back
on-line I got a message saying the port (Com 1) was in use. Several tries
and rebooting got the same error. After panicing for a while, I hooked up
an external modem to Com 1 (only com port). Same error. I went to device
manager and disabled the internal modem and enabled the external. Seems
to be working again.
Lightning ate internal modem? I hate to leave my expensive US Robotics
external modem exposed to the same fate. I'll look in my emachine and see
if a slot is open, and my old computers and see if I have a modem that
fits. If not, and I have a slot, probably a new cheap Winmodem. Are there
cheap USB external modems now?
Other suggestions?
.
- References:
- Modem problem
- From: Ken Knecht
- Modem problem
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