> Date:    Fri, 2 Jul 1999 23:33:16 -0500
> From:    Mike Buraczewski <[log in to unmask]>
>
> Ben
>
> I just finished up with the exact same thing on my son's modem.  The thing
> that finally told me that we had a snafu modem was that when we plugged the
> telephone into the modem, it would give a dial tone, but would not hang up.
> Everything else tested out fine.
>
> I suggest that you replace the modem.
>
> Mike Buraczewski
> [log in to unmask]
> -----Original Message-----
> From: Ben Moore <[log in to unmask]>
>
> >Greetings,
> >
> >I have a problem with a modem on a friend's computer.  Last night the modem
> >was working correctly.  Today it gives a "no dial tone" response with both
> >dial-up networking and HyperTerminal.  Nothing has been done to the
> computer
> >during that time period.
> >
> >This an older Compaq 486 with Win95b and  a Cirrus-Logic 33.6 modem
> >installed.
> >
> >Device manager shows the modem installed and working correctly, no
> >conflicts.  Modem diagnostics gives a full report that looks ok except for
> a
> >"no response" to the AT15 command. I'm not really sure what the diagnostics
> >should look like for this particular modem.  You can hear it dial if you
> >disable "wait for dial tone" so at least part of it is working correctly.
> I
> >have confirmed dial tone to the connector on the modem.  I have reinstalled
> >the modem.
> >
> >We had storms in the area last night but nothing very close and both the
> >power and  telephone line are supposedly protected by a cheaper surge
> >protector.
> >
> >I'm out of things to try.  It looks to me like a defective modem.  Any
> >suggestions would be appreciated?  Thanks.
> >
> >Ben Moore
> >
> >                Curious about the people moderating your
> >                   messages? Visit our staff web site:
> >                     http://nospin.com/pc/staff.html
> Date:    Fri, 2 Jul 1999 23:11:49 -0400
> From:    Jim Meagher <[log in to unmask]>
> Subject: Re: Modem Problem - no dial tone
>
> Ben,
>
> Have you tried plugging a telephone into the circuit?
> If the phone has a dial tone and the modem can not detect it,
> then the modem is fried.
>
> Jim Meagher
> =====
> Micro Solutions Consulting        Member of The HTML Writers Guild
> http://www.ezy.net/~microsol     International Webmasters Association
> 410-543-8996                MS Site Builder Network - Level 2 member
> =====
> ----- Original Message -----
> From: Ben Moore <[log in to unmask]>
>
> > Greetings,

<SNIP - see above>

Assuming that the modem is no longer under warranty (either by the
manufacturer or the maker of the surge protector), it *might* be
salvageable by someone who is good with a soldering iron.  Do either of
you know somebody like a radio ham?  I am not suggesting that it would be
cost effective even if you only paid yourself $0.50/hr, but it might be
interesting.  (Without schematics, or at least pinouts for major components,
even the best technician is just shooting in the dark.)

It seems as if one modem has the electromechanical relay that connects it
to the telephone line stuck in the ON position (dial tone), while the
other is stuck OFF (no dial tone).  Relays are notorious for causing
problems (Look up the story of the the original computer "bug" - it got
caught in a relay.).

A current surge could have welded the contacts together in the ON position.
Try tapping the relay with the handle of a screwdriver or the like.  A good
whack could jar the contacts loose.  If not, you could hunt down a
replacement and repair it.  Make sure that the signal that switches the
relay coil off and on switches - a transistor (hopefully on a small-scale
IC) could be blown short.  That could be replaced, too.  It is common for
coils (such as the relay coil) that are subjected to rapid current surges
(either spikes or rapid power mains switching - such as could be caused by a
distant lightning strike) to develop voltages that are high enough to
damage transistors.

[When I was 10, I connected a 1.5 V "D" cell (ordinary flashlight battery)
to a rather large solenoid coil.  So far, no problem.  Current flowed, and
wanted to keep flowing.  When I broke the connection, I drew an arc that
was about 1/16 inch long before the current found an alternate route -
through ME!  Hand to hand, across the chest, that was a truly memorable
ZAP!]

You could try using a magnet to close the relay that is stuck open.  If
that works, then either the relay coil is open (In this case, the voltage
across the coil will switch ON when you tell the modem to connect, and OFF
when you hang up.), or a transistor is blown open (see above).

Have fun!

Boyd Ramsay

[log in to unmask]

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