strange problem after power surge/thunderstorm
Faheem Mitha
Last night there was a thunderstorm in the vicinity. During the
lightning flashes, my modem (Robotics 56K) went out and refused to
reconnect. When I tried to dial out using a regular phone, I just got
static on the line. I talked to the phone people, who said I should
try disconnecting everything that was connected to phone lines and
reconnect. I have a modem hooked in to one phone jack and a phone
hooked into another phone jack (same line).
So I unhooked both the phone and the modem, and when I put the modem
back, it worked.
However, once I hung up the modem, it refused to reconnect till I
disconnected the modem from the phone jack and reconnected again. I
left my regular phone disconnected to simplify matters.
Now, I'm not sure what the problem is. My first thought is that the
modem is damaged. I've hooked in an old modem into the computer and it
seems to work normally when I disconnect and reconnect etc.
The ironical thing is that I hooked the modem up through a APC
Surgearrest (Pro8), and followed the instructions as far as I could
tell. But this happened anyway.
Would it be reasonable to assume that the problem here is a defective
modem? I think I will go ahead and ask for the cost of my modem from
APC in any case, and see what happens.
As far as I can see, my computer is otherwise working normally.
Please feel free to cc me on any reply to fah...@email.unc.edu.
Faheem.
Franc Zabkar
<fah...@email.unc.edu> put finger to keyboard and composed:
>Dear People,
>
>Last night there was a thunderstorm in the vicinity. During the
>lightning flashes, my modem (Robotics 56K) went out and refused to
>reconnect. When I tried to dial out using a regular phone, I just got
>static on the line. I talked to the phone people, who said I should
>try disconnecting everything that was connected to phone lines and
>reconnect. I have a modem hooked in to one phone jack and a phone
>hooked into another phone jack (same line).
>
>So I unhooked both the phone and the modem, and when I put the modem
>back, it worked.
>
>However, once I hung up the modem, it refused to reconnect till I
>disconnected the modem from the phone jack and reconnected again.
It appears that the modem's hook relay contacts are stuck in the
closed (off-hook) position. If this relay is an electromechanical
type, and if you are handy with a soldering iron, then a replacement
should cost you less than $5.
-- Franc Zabkar
Please remove one 's' from my address when replying by email.
Faheem Mitha
Could this have been caused by a power surge, or is it most likely
unrelated? I am asking in case APC argues it was not their fault.
I barely know what a soldering iron is, don't know anything about
electrical gadgets in general, and in any case don't have the time for
projects like this right now.
Thanks. Faheem.
w_tom
Franklin did in 1752. He diverted a surge to earth so that it
would not find destructive path via church steeple. That is
also what a surge protector does when it is effective. 'Whole
house' surge protectors are effective because an incoming
surge is earthed before it can enter the building. Plug-in
surge protectors have all but no earth ground meaning no
effective surge protection. They are called shunt mode
devices. They don't stop, block, or absorb surges. They are
only effective when as shunts - temporary short circuits less
than 10 feet to earth during the surge.
How to identify ineffective surge protectors - no dedicated
connection to central earth ground AND they avoid all
discussion about earthing. No earth ground means no effective
surge protection. No earth ground means the surge protectors
cannot divert - shunt - the surge. A surge permitted inside
the building will seek every path to earth, often
destructively, via appliances.
A phone line typically has 'whole house' surge protection
provided free by the telco in a premise interface box - often
called NID. That 10 AWG wire connects less than 10 feet to
central earth ground. But AC electric (wires highest on the
pole and therefore most often struck) is the most common
incoming source of surges. You have seen the problem.
Incoming on AC electric, through modem, to earth ground via
phone line. (Measure a direct connection from one AC prong to
some pins on modem IC). First a complete circuit must be
created. They something is damaged in that surge.
Franc Zabkar has defined one most common part damaged by
surge. Another is the PNP transistor that drives that relay.
Those relays have since been upgraded with new part numbers
because they are now more resistant to a surge from relay coil
to relay wiper - from 500 volts to 1000 volts.
Demand that APC provide new modem. They provide a
warranty. Hold them to it. In the meantime, address future
surge solutions by installing 'whole house' surge protectors
or by directly earthing to single point ground every incoming
utility. Your single point earth ground should meet or
exceed post 1990 NEC requirements. A surge protector is only
as effective as its earth ground - which APC avoids even
mentioning. No earth ground means no effective surge
protection.
Faheem Mitha
Thanks for the discussion. If these surge protectors are so useless,
why does APC sell them, why does anyone buy them, and why haven't they
been sued out of business long ago (or something)?
Can you provide any further good references (preferably on the net) to
`whole house' surge protectors and/or `directly earthing to single
point ground every incoming utility'? I don't know anything about
this, and assumed the conventional wisdom was correct in this
case. Thanks.
Faheem.
w_tom
naive buy Listerene? Why does GNC sell supplements in 5 and
50 times the required daily dosages? Why do plug-in surge
protector's sell? Same reasons.
How many days of reading do you want. Engineers discussed
basic concepts on residential surge protection extensively in
the newsgroup misc.rural :
Storm and Lightning damage in the country 28 Jul 2002
Lightning Nightmares!! 10 Aug 2002
Other newsgroups where surge protection has been discussed:
uk.d-i-y
Lightning protection 28 Oct 2002
microsoft.public.backoffice.smallbiz2000
OT: Power surge protectors for workstations 7 Feb 2003
comp.home.automation (grounding discussions)
Whole House surge suppresor....for the millionth time! on
29 Sept 2002
Ground rods on 21 Aug 2002
rec.radio.shortwave
Some Lightning Effects Related Questions ? 24 Aug 2002
rec.radio.amateur.antenna
single point grounding Extensive posts thru Jul 2001
Grounding Question - Connecting to Power Ground 7 May
2001
(especially posts from Richard Harrison)
rec.video.satellite.dbs
Grounding? Best way to hook up dss -- 4 Aug 2001
Surge protector enough for lightning strike ?? 2 Jul 2001
rec.video.satellite.tvro
more ideas on lightning protection 15 Aug
Why is lightning taking out my LNB's? 11 Aug
Benchmark in surge protection is Polyphaser. Their
engineering and application notes are considered legenary by
industry professionals (however some need read them multiple
times to understand):
http://www.polyphaser.com/ppc_technical.asp
Surge protections is so reliable and so easily installed that
surge damage is considered human failure:
http://scott-inc.com/html/ufer.htm
http://lists.contesting.com/_towertalk/1997-April/004413.html
http://www.harvardrepeater.org/news/lightning.html
> Well I assert, from personal and broadcast experience spanning
> 30 years, that you can design a system that will handle *direct
> lightning strikes* on a routine basis. It takes some planning
> and careful layout, but it's not hard, nor is it overly
> expensive. At WXIA-TV, my other job, we take direct lightning
> strikes nearly every time there's a thunderstorm.
http://www.traceengineering.com/technical/tech_notes/tn7.html
> The first step in inverter protection is to make sure that all
> equipment in the system is physically grounded at the same
> location. [Figure 1 examples bad, multi-point grounding.]
Concepts of earthing with examples of earthing for more
reliable operation:
http://lists.contesting.com/_towertalk/2000-August/032935.html
> What you're proposing to do has the makings of what is referred to
> as a Ufer ground. Named for its inventor, the principle of the
> Ufer ground is simple. ... according to Polyphaser's "Grounds
> for Lightning Protection" publication.
http://www.erico.com/erico_public/pdf/fep/TechNotes/Tncr002.pdf
http://www.comm-omni.com/edcoweb/grndw.htm
[section entitled "Measuring Ground Resistance at Cellular
Sites,Microwave and Radio Towers"]
http://www.leminstruments.com/pdf/LEGP.pdf (ground
network on page 14) [or]
http://leminstruments.com/grounding_tutorial/html/index.shtml
Example of how a surge protector is connected including the
requirements for a less than 10 foot connection to central
earth ground:
http://telebyteusa.com/catalog/manuals/m0161.htm
http://www.telebyteusa.com/primer/ch6.htm (see Section
6.4)
> Conceptually, lightning protection devices are switches to ground.
> Once a threatening surge is detected, a lightning protection
> device grounds the incoming signal connection point of the
> equipment being protected. Thus, redirecting the threatening surge
> on a path-of-least resistance (impedance) to ground where it is
> absorbed.
Sun Server Planning Guide (see Adobe page 89):
http://www.sun.com/servers/white-papers/dc-planning-guide.pdf
> Lightning surges cannot be stopped, but they can be diverted. The
> plans for the data center should be thoroughly reviewed to
> identify any paths for surge entry into the data center. Surge
> arrestors can be designed into the system to help mitigate the
> potential for lightning damage within the data center. ...
How modems are damaged:
newgroup alt.home.repair
"Whole house surge protector" 14 Jun 2002
First damage observed:
newgroup comp.dcom.modems
"Can't detect dial tone" on 16 Jul 2001 by Franc Zabkar
http://groups.google.com/groups?selm=3b522d5a.241230%40news.dingoblue.net.au
After second damage:
newsgroup comp.dcom.modems
"Lightning Strike Damage Report" on 10 Dec 2001
http://groups.google.com/groups?selm=3c127fb2.3326501%40news.dingoblue.net.au
Later repeats his conlusions:
newgroup comp.dcom.modems
"Lightning strike screwed up my USR courier! help ple..."
http://groups.google.com/groups?selm=3cc28cb4.13201880%40news.dingoblue.net.au
> I was originally a skeptic until my friend's house suffered a
> direct strike. I analysed the damage and posted my results here: