Modem not getting dialtone

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I live in a rural area and can only get dialup internet, unless I was
to get a very costly satellite. The dialup is slow but works. This
is just one of the prices we pay to live in a rural area, but I'll
live with the slow internet rather than live in any city.

The other problem about living in a rural area is that lightning can
travel long distances and destroy modems. I lose at least one modem
every year. I unplug them from the phone line when not in use, and
this prevents most modem losses, but there is always the unexpected.

Last night I saw a storm approaching on the radar map, but it was
still a distance away. Suddenly out of nowhere, I saw a bright flash
of lightning from my window, and my modem immediately dropped
connection. That's all it took to ruin another modem, even though the
lightning was still miles away.

Its a USR Courier 56K external V-everything. When I click on my
dialer, the modem tries to connect, makes a sick sound from the
speaker, but brings up a message that says no dialtone. Yet the phone
(connected to the phone jack on the back of the modem) works fine.

I have a background in electronics but rarely work on the stuff
anymore. I realize these modems are not really repairable in most
cases, but I opened the case and am looking at the MOV on the board
near the phone line jack connection. I know they are supposed to
protect the modem from lightning and other surges. Could this MOV
have simply shorted out internally? How can I test the MOV using a
multimeter? Or should I just remove it and see if the modem works
without it? (of course I would replace it if the modem did work).

I doubt it's this simple, but I thought I'd spend a short time trying
to repair ir before tossing it in the trash.

By the way, the modem I am using now, is identical. This one was
working well several years ago, the computer was off, but the phone
line was still connected to it. After a lightning storm, this 56K
modem now would not connect above 24K. I just use it as a spare until
I can get another one on Ebay or something.

Thanks for all help.

 

[Martin Brown]

I live in a rural area and can only get dialup internet, unless I was
to get a very costly satellite. The dialup is slow but works. This
is just one of the prices we pay to live in a rural area, but I'll
live with the slow internet rather than live in any city.

The other problem about living in a rural area is that lightning can
travel long distances and destroy modems. I lose at least one modem
every year. I unplug them from the phone line when not in use, and
this prevents most modem losses, but there is always the unexpected.

Last night I saw a storm approaching on the radar map, but it was
still a distance away. Suddenly out of nowhere, I saw a bright flash
of lightning from my window, and my modem immediately dropped
connection. That's all it took to ruin another modem, even though the
lightning was still miles away.

Its a USR Courier 56K external V-everything. When I click on my
dialer, the modem tries to connect, makes a sick sound from the
speaker, but brings up a message that says no dialtone. Yet the phone
(connected to the phone jack on the back of the modem) works fine.

I will hazard a guess that the lightning strike took out the transistor
that takes the line off hook. I don't know why that is the most common
failure mode, but I have seen it before with a high end Boca modem.
Symptoms exactly as you describe. Replacing the right transistor might
well be a cure. Might be worth asking in the modem specific groups in
case someone with that modem has seen and fixed the same fault.

You should probably invest in a much more chunky antisurge device to a
good Earth return on your phone line if this is an annual event.

I have a background in electronics but rarely work on the stuff
anymore. I realize these modems are not really repairable in most
cases, but I opened the case and am looking at the MOV on the board
near the phone line jack connection. I know they are supposed to
protect the modem from lightning and other surges. Could this MOV
have simply shorted out internally? How can I test the MOV using a
multimeter? Or should I just remove it and see if the modem works
without it? (of course I would replace it if the modem did work).

I doubt it's this simple, but I thought I'd spend a short time trying
to repair ir before tossing it in the trash.

My money would be on the transistor that drives the off hook relay. Do
the indicator LEDs do anything unusual on the bad modem?

By the way, the modem I am using now, is identical. This one was
working well several years ago, the computer was off, but the phone
line was still connected to it. After a lightning storm, this 56K
modem now would not connect above 24K. I just use it as a spare until
I can get another one on Ebay or something.

Force a V34+ connection and you will be better off. There will be an
init string to do this hidden somewhere in the documentation.

Regards,
Martin Brown

 

[Dennis]

I will hazard a guess that the lightning strike took out the transistor
that takes the line off hook. I don't know why that is the most common
failure mode, but I have seen it before with a high end Boca modem.
Symptoms exactly as you describe. Replacing the right transistor might
well be a cure. Might be worth asking in the modem specific groups in
case someone with that modem has seen and fixed the same fault.

You should probably invest in a much more chunky antisurge device to a
good Earth return on your phone line if this is an annual event.

I had a friend that lost several modems in a rural area. She talked to
the phone company about it and the first guy looked at the connection
and said there was nothing they could do. After another modem she called
again and the gal they sent out said the ground connection was crap. She
put in another ground rod and redid the connections. No more dead modems
even after several storms like the ones that destroyed previous modems.

On another note she used one of those surge suppressors that said they
would replace damaged devices plugged into it. She brought in the
remains of the modem and surge suppressor and they did do a replacement.
(I forget the brand.)

 

[Martin Riddle]

I had a friend that lost several modems in a rural area. She talked to
the phone company about it and the first guy looked at the connection
and said there was nothing they could do. After another modem she
called again and the gal they sent out said the ground connection was
crap. She put in another ground rod and redid the connections. No more
dead modems even after several storms like the ones that destroyed
previous modems.

On another note she used one of those surge suppressors that said they
would replace damaged devices plugged into it. She brought in the
remains of the modem and surge suppressor and they did do a
replacement. (I forget the brand.)

I was going to recommend a Power strip and surge protector with a data
port protector.
They do have a guarantee.
I have a old Sportster 28.8 and a Courier 56K(grey) that I can live with
out, let me know (OP) if your interested.

Cheers

 

[Martin Brown]

MOV devices can degrade or go bad due to over-voltages, so yes, that is
something you could replace at low cost; not worth testing in light of
your experience and comments.

The MOV inside the modem is too close to the electronics and too feeble
to do any good. The failure mode is almost always of the unfortunate
transistor that drives the off hook relay (cheap and easy to replace on
some boards harder on surface mount designs). The MOV may also be dead
and better off being removed but isn't worth replacing.

You want a really chunky surge arrester on a thick copper strap to a
good solid ground spike near where the phone cable enters the property.

To test, you would need to lift one lead for a multimeter test which may
or may not be useful.
Say the MOV was rated at 100V breakdown and the surge decreased that to
40V (below the phone open circuit battery voltage).
The multimeter would show an open and thus imply the MOV to be OK when
it ain't.

I recommend you replace it without a second thought.

I expect the off hook transistor saved the MOV by dying itself. We used
to see quite a few interesting lightning induced faults this time of
year. Typically with inter building underground cables even the big
protectors could not always be relied upon to do their job and interface
boards were often casualties of a direct building hit.

Once so was our phone system when the main conduit wiring was turned
into a stripe of charred mess on the wall. The switchboard girls were
inconsolable - it went with hell of a bang. Turned out copper thieves
had pinched the external lightning conductor.

Regards,
Martin Brown

 

[bud--]

Nobody ever stops a surge. Any protector adjacent to that modem can only
vainly try to stop the surge.

The latest in westom's crusade to save the universe from the scourge of
plug-in suppressors.

Unfortunately for westom, nobody agrees with him.
Both the IEEE and US-NIST say that plug-in suppressors are effective.

Then go find a ‘whole house’ protector from responsible companies
such as Leviton, Intermatic, GE, Siemens, ABB, or Square D.

Service panel suppressors are a real good idea.
But from a surge guide published by the NIST:
"Q - Will a surge protector installed at the service entrance be
sufficient for the whole house?
A - There are two answers to than question: Yes for one-link appliances
[electronic equipment], No for two-link appliances [equipment connected
to power AND phone or cable or....]. Since most homes today have some
kind of two-link appliances, the prudent answer to the question would be
NO - but that does not mean that a surge protector installed at the
service entrance is useless."

The NIST surge guide suggests that most equipment damage is from high
voltage between power and phone or cable wires (could have been the OP's
problem). Service panel suppressors do not prevent that high voltage
from developing (but are likely to protect equipment connected only to
power wires).

(If using plug-in suppressors all interconnected equipment needs to be
connected to the same plug-in suppressor. External connections, like
phone, also need to go through the suppressor. Connecting all wiring
through the suppressor prevents damaging voltages between power and
signal wires.)

All westom's "responsible companies" except SquareD make plug-in
suppressors and say they are effective.

SquareD says for their "best" service panel suppressor "electronic
equipment may need additional protection by installing plug-in
[suppressors] at the point of use."

That means you always inspect your earthing to both
meet and exceed post 1990 code.

Nothing significant for earthing happened in the 1990 NEC.