Power from Desktop ethernet port damaging modem?

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Sournotev2

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Jun 16, 2014
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I work in IT and I have a client telling me her cable service provider is saying that her network problems are caused by power flowing from her ethernet port, through her ethernet cable, into (presumably) her modem, which is causing network disruptions throughout her house.

My question is: Is this possible? I have never heard of this and am having difficulty finding any material on this sort of situation. My intuition would be motherboard issues but I've had enough experiences with shoddy cable company inspectors to by skeptical.

Hoping I'm posting this in the correct section. Thanks for any clarification that anyone might be able to provide.

EDIT: After finalizing my account and browsing more, I do believe I posted this in the wrong section. If anyone with the authority to help me out here sees this, feel free to move this question to the appropriate category for me.
 
Solution
smorizio
I been a tech for a long time and some strange issue can pop up. I seen lighting take out a lot pc from backfeeding frm cable modem into the ethernet ports of pc plugged in. I also seen bad cable boxes screw up a whole household. also bad cable wires and or splitters. your first test should be if you unplug her pc from the home does the home network work.
if it does...use malware bytes and a anti virus to see if she infected. also try booting from a windows installer or hirem mini xp disk...to see if the error still there. if it is,try using a wifi or another network card. also look to see if any of the metal backplate of the case is inside the Ethernet port. on other thing check to see she using the right cable. some ethernet cables...
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hunter315

hunter315

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May 12, 2009
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1. Assume all cable tech support is lies
2. Assume all cable tech support came from idiots

Now that we have the basics out of the way. There is a protocol for Power Over Ethernet(PoE), but it is generally not supplied by a motherboard, the power generally comes from a router, switch, or access point and can be turned on or off for each port individually.

A couple possible solutions to this, first being try a different router, but i provide a different option before then. Does this only occur at a certain time of day? I recently moved to a region where the power company polls the meter through communication over the power lines, this just fills the power line with slime for about an hour making my internet rather spotty until they are finished, if they do that in her region she may get similar results.
 
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smorizio

smorizio

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Jan 22, 2010
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I been a tech for a long time and some strange issue can pop up. I seen lighting take out a lot pc from backfeeding frm cable modem into the ethernet ports of pc plugged in. I also seen bad cable boxes screw up a whole household. also bad cable wires and or splitters. your first test should be if you unplug her pc from the home does the home network work.
if it does...use malware bytes and a anti virus to see if she infected. also try booting from a windows installer or hirem mini xp disk...to see if the error still there. if it is,try using a wifi or another network card. also look to see if any of the metal backplate of the case is inside the Ethernet port. on other thing check to see she using the right cable. some ethernet cables are cross over some are straight through. also most of the newer routers need the higher 5/6 cat cables if you want gigbit speeds. also if her home was hard wire with wall plugs...check the cables and plugs see that they were wired right. there are for a few dollars port checkers.
 
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Sournotev2

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Jun 16, 2014
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FOLLOW-UP: Hey guys, thanks again, I was much better prepared to help this woman out.

Checked her cable, it was an ethernet cable, not a crossover.
Opened up her Dell Desktop, and found a capacitor that was tipped over, leaning against and physically contacting the metal (what metal is that? Aluminum?) housing of the ethernet port. My best guess is that power is being ran through that capacitor, through the metal housing, and then through the ethernet cable and into her modem.

I work in an awful retail department and so my only option was to recommend her a 200-300 dollar "hardware service center". She asked for a "band-aid" solution and I sold her a wifi adapter. Boss chewed me out about it but I even opened it up and installed it for her to show her it would get her through the short-term.

I also cautioned her that as this was motherboard issue, it was only likely to get worse.

Was this the best solution for her? My boss doesn't know anything about computers, so feedback is appreciated.
 
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smorizio

smorizio

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Jan 22, 2010
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if the cap is hitting the io shield. if can sometime be fixed if the mb was installed to far to the rear of the case. sometime you can losen the standoff screws and sometime slide the mb back. the other option to help her is take a photo of the issue and contact dell customer relations if the unit is out of warranty and show them the defect that was found. ask them to send a replacement mb under a one time rma. also have her or you google that dell model info see if there any recall on that defect. if dell wont help the non warranty dirty fix would be to pick up a piece of shrink tubling slide it over the cap and shink it in place to keep it from shorting to the case.
http://www.allelectronics.com/make-a-store/category/265/heat-shrink-tubing/1.html
 
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