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.
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.
My money would be on the transistor that drives the off hook relay. Do the indicator LEDs do anything unusual on the bad modem?
Force a V34+ connection and you will be better off. There will be an init string to do this hidden somewhere in the documentation.
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.
The MOV on the modem (or any MOV adjacent to that modem) cannot protect from a type of transient that typically causes damage and that has apparently caused your damage. Your symptoms are typical of damage found in most modems. Generally, a PNP transistor drives the off-hook relay (from +5V to relay coil). If that transistor is shorted or open, then the ?No Dialtone? message is expected.
First, using a multimeter, that transistor that drives the off-hook relay can be checked. With a soldering iron and a very stable hand, that transistor can be replaced.
Another less likely suspect is low value resistors often found between the modem and phone line. Again, a meter can easily check those.
Second, moving on to why you have damage. All phone line must have a 'whole house' protector installed for free. If that subscriber interface protector is properly earthed, then no surge enters on a phone line. Properly earthed means a short (ie 'less than 10 foot') connection from the protector to single point earth ground. An earthing electrode that also connects just as short to every wire inside every incoming cable. For example, TV cable also must be connects just as short to the same earth ground. Otherwise all household protection is compromised.
If all wires connect to earth, then no energy is inside hunting for earth destructively via appliances (ie your modem). If any one wire inside any utility cable does not connect to earth, then energy is hunting for earth destructively inside via appliances. Nothing will avert that hunt.
Three AC wires enter. One (neutral) should already make that short connection to earth. Other two (hot) wires have no earthing if you did not install a 'whole house' protector. So a distant lightning strike connects incoming to every appliance inside the house.
A surge is called electricity. It is incoming to everything. But it also must have an outgoing path to earth. If both paths do not exist, then no damage. What is a best outgoing path to earth? That telco 'installed for free' protector. A best path is incoming through a computer, through modem's off hook relay transistor, through off hook relay, out the phone line, and to earth via the subscriber interface protector. Your damage is due to a human failure because at least one wire entered without first connecting to earth.
Those hot AC wires are the most common source for incoming surges. You cannot earth it directly like the TV cable or neutral wire. So you must earth it via a 'whole house' protector.
Third, why is the modem a best path to earth? Early modem off-hook relays provided galvanic isolation up to 500 volts. Therefore a best path to earth was via its PNP transistor, into the relay coil, and out to earth via relay contacts. Later version modems (ie yours) would have an off-hook relay of 1000 volts. Still a best and destructive path to earth.
Nobody ever stops a surge. Any protector adjacent to that modem can only vainly try to stop the surge. More often gives a surge even more destructive paths to find earth. Effective protection is always and only earthing that energy before it enters the house. You have no other alternative. Cable TV and telephone should already be connected to earth. But AC electric almost never is. AC electric is the most common source of incoming surges through modems.
If the incoming surge was not earthed before entering, then that surge will select appliances to find earth destructively.
Finally, start here. Up top was what is most likely damaged. A multimeter should identify that failure either in ohms when the modem is not powered or using DC volts when modem is powered. Chances are every modem will work just fine (like a few of these 56K modems I have fixed) for years.
Then go find a ?whole house? protector from responsible companies such as Leviton, Intermatic, GE, Siemens, ABB, or Square D. A Cutler-Hammer solution sells in Lowes and Home Depot for less than $50. The only effective protectors always have that dedicated wire for single point earth ground. That means you always inspect your earthing to both meet and exceed post 1990 code. The most critically important of all is the earthing.
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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.
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.
Could he just take the MOV out and see if his connection rate improves to 56K. MOV's can make a lot of electrical noise after they get whacked a few times (that's a technical term, by the way). And if it improves, then go buy another modem. Probably cheaper at a flea/market, swap shop than ordering an MOV by email. Sad, but true.
Also, I would be remiss if I did not mention the first two things that popped into my mind when I heard the words "modem, lightning, and poor connection" all in the same thread.
1) 1488 and 1489 serial line drivers/receivers are NOTORIOUS for going bad.
2) The replacement modem might require a different setup command string. If I had a nickle for every "Hayes-Compatible" problem I ever came across, I wouldn't be posting here, I can assure you. Unless they have Internet connections in the Seychelles, that is. (And I get truly bored!) :)
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.
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.
His error message is No Dialtone Detected. That means either the MOV shorts the phone line (no phones work in the house). Or the modem is disconnected from the phone line. 1488/1489 drivers would be working. The No Dialtone Detected message comes from the motherboard computer talking to the modem's computer. If 1488/1489 drivers were damaged, the error message would be no modem detected. The computer is talking to the modem's computer just fine.
Problem is between that modem's computer and its phone line (assuming other phone do work). Most often a PNP transistor that drives an off-hook relay. A simple fix as long as that transistor is not part of an IC that contains the modem's computer. And a problem averted in the future by addressing the most common source of that damage: AC electric wires entering without a connection to earth.
MOV is only for minor voltage differences between phone wire pair. During a typically destructive surge, that voltage difference is tiny or near zero also due to an existing subscriber interface protector and due to the type of transient that does damage.
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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.
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."
Nothing significant for earthing happened in the 1990 NEC.
Tempted to preach about grounding. The ground for your telephone system should be the same as for your AC mains. If they are different, you'll get a garranteed high voltage for almost any energetic lightning.
Can you tie them at the same place, at the access point to your home?
Also, why not add your own 'protection' network right where your phone line plugs into the modem. Make shield metal box that bolts to your PC metal. Inside the shield box you can 'copy' the RFI/EMI line filter schematic. But do NOT connect the GND/Shell to the GND of your box, that will be too much capacitance for your phone system, instead put it on a sheet of plastic and at each corner of the box, solder in
100V tanzorb [they're fast] The idea is that the maximum voltage that can ever get in there should be easy for the modem's protection to handle, not the couple of thousand volts that might be appearing.
But, again, improve GROUND. then try additional protection.
I know it's possible to keep destructive transients out by adding a box to re-reference the phone line right at your PC. I used to do these techniques to protect TTL control logic in a 200kV arcing/ sparking system.
Seriously though, if you don't have ground for phone and ground for AC mains the same, you are asking for major problems if you get a real direct hit at your home.
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