I keep burning out modems and I got shocked

September 1, 2010 at 09:07:00
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I had a DSL modem that got burned out and was replace which also burned out. I switched to a cable modem and it also got burned out. I also got shocked when i touched the modem cord plugged into the surge protector. I changed surge protectors 3 times. I had an electrician check the house wiring and he said the panel and the outlet was good. The computer and the printer are also plugged into the surge protector and have had no problems. There is a lamp plugged into the outlet that the surge protector is plugged into and no problems there either. The only common point is the lan connection from the pc to the modem. Is it possible for electricity to feedback from that port to the modem enough to burn and the modem and cause a shock just from touching the cord?

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September 1, 2010 at 09:19:14
A surge protector provides no protection from shocks. A GFIC does.

What else were you touching when you were shocked? Highly unusual to get a shock from an insulated cord unless dealing with high voltages like you get with an electric fence.

Network lines run at about 2 volts which isn't much.

Did the electrican run a load test on the circuit? He should have.

Power supplies usually burn out not from too much power [surge] but too little power [brownout]. If you have say your refrigerator, for example, and the rest on this one circuit you may be under powered and that is why they are burning out.

Did the electrican check the circuit breaker grounding? Code these days is to have two ground rods 10 ft apart. Part of your issue may be improper grounding of the electrical panel. This is common in dry climates.

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September 1, 2010 at 09:23:05
This could happen, when computer and modem are connected to different outlets, that may use different electrical phases. When touching the computer with one hand and holding the metallic connector of the network cable in the other hand, you can feel a bit of tickle.
Better is to messure the current between the computer case and the network cable.

The original poster should always write the last response !!!
Let us know, if the problem is solved !!!

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September 1, 2010 at 10:24:42
It's possible, but not likely--I've had a reversed polarity outlet on one terminal connected to a network blow terminals connected much further down the line. This was a reversed polarity (live/ground) on an outlet other than the one connected to the destroyed machine.

You should not get shocked when you touch the mode power cable!

Check the outlets for all equipment which attaches to the LAN cable. (Get a cheap checker from the hardware store, looks like a plug w/o wires, yellow, has led's that indicate the wiring, made by GB. Assuming you're in US, not sure what they look like elsewhere. Get one, use it every time you plug something into a new outlet, it will save you grief.) This includes the wall outlets AND the outlets on any surge protector/distribution strips. Have any incorrect sockets rewired.

If you have (good to have) a multimeter, check to verify that the voltage going into the modem is correct (both voltage and polarity +/-.

If it's easy to check the cables physically, do that first. If it appears worn replace it--if it's a short cable replace it at least temporarily.

Does this happen:
1) When only the modem power cable is plugged in? (i.e. the modem isn't connected to power.) If so, the problem is probably with the wiring inside the surge protector. Check to make sure the wiring is correct/replace if not.

2) When the modem power cable is plugged into the modem, but the LAN is disconnected? This indicates a fault inside the modem, unlikely since you've had several burn out. Cure is to replace the modem.

3) When the modem power cable is connected, the modem is powered and the LAN cable is connected ONLY at the modem? This indicates a problem with the LAN cable itself, and you should inspect/replace the cable..

4) When everything is connected, but the modem power supply is not plugged into the outlet? This indicates that the problem may be with the computer or other device attached to the LAN cable. The computer may have a grounding problem, to check it, you need to check for voltage between the chassis and the outlet ground-it should be zero.

Check the Lan cable wires individually for voltages by putting the ground (-) lead to the outlet ground. None of the wires should show anything over about 12-25 volts.

If you find voltages higher, then you need to inspect the cable to see if there are any breaks, if the cable were abraded and contacted a live 110/220 circuit, it would cause the problem.

In general, to troubleshot this kind of thing, start at the power and verify each piece of the system (outet, surge protector, modem power supply/cable, modem, LAN wire and other connected devices.)

Hope this helps.

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