Re: Weird modem problem
- From: w_tom <w_tom1@xxxxxxx>
- Date: Thu, 31 May 2007 18:14:06 -0700
On May 31, 2:06 pm, Charlie Wilkes <charlie_wil...@xxxxxxxxxxxxxxxxxx>
wrote:
Thanks. This squares with what happened yesterday. When I lost the
dial tone as I described, I was attempting to test the line with a phone
that has an LCD display that is non-functional because it needs 3 AA
batteries, which I hadn't bothered to install.
What I heard was a repetitious clicking sound, and with each click, the
LCD display became visible for a moment... some kind of pulsing current.
The bottom line is that the damn phone company fried my internal Win
Modem. I think I'm gonna complain to the FCC, because this is not the
first problem I have had at this location.
How many actually fixed modems to learn what fails and why? Your
symptoms are classic of a common modem failure. First, phone lines
already have a 'whole house' protector installed free by the telco
where their wires meet yours. If you have provided that protector
with superior earthing, then surges on phone line would be earthed
long before geting to the modem.
Remember how electricity works. First a surge forms a complete
electrical path from cloud, through electronics, to earth. Then
current flows through everything in that path. Current does not flow
like a wave crashing on the beach. Current flows through everything
in that path simultaneously. Finally something in that path fails.
A typical path to earth ground is via wires taht are more exposed
and that don't have an earthed 'whole house' protector. Surges enters
on AC electric to pass through computer. Current exits via modem
(both an incoming and outgoing path must exist). Then to ground via
phone line.
What gets damaged? A common failure is a PNP transistor that drives
the modem's off-hook relay. If the PNP transistor is blown, then the
computer will respond with 'no dial tone detected' - never connect to
phone line. However if it was a lesser surge, then the transistor
may only short - always on. As long as computer powers modem, then
modem acts like a phone off the hook. Dial tone is lost - just like a
phone left off the hook. And again, computer would complain of 'no
dialtone detected'.
Telco did not do this damage. You are responsible for earthing
every utility wire to a common electrode before those wires enter the
building. That means your AC electric earthing must be upgraded to
meet and exceed post 1990 NEC requirements. That means every wire in
every utility cable must connect 'less than 10 feet' to that common
earthing electrode. Connection either via a protector (AC electric
and telephone), or via a direct hardwire connection (satellite dish
and Cable TV).
Remember, a protector is not protection. That telco provided 'whole
house' protector is only effective IF earthed 'less than 10 feet' to
same electrode used by AC electric and other utilities. If not, then
a surge may find earth ground, destructively, via your modem.
Some have posted "There is probably some kind of ..." IOW he is
guessing. This post is based on tracing surge damge by literally
replacing damaged parts soldered on circuit boards. If you let a
surge into your building, then it may find earth ground, destructively
via a PNP transistor and off-hook relay on that modem.
Most common source of damage to fax machines, modems, portable phone
base stations and answering machines: incoming on AC electric and
outgoing to earth ground via phone line (and the telco installed
protector). Damage directly traceable to surges that were not earthed
before entering a building. That incoming path can be anything
including cable and satellite dish.
.
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