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Question Unmanaged Ethernet Switch (not PoE) - Leakage current / voltage of 65V AC

S

ssimlai

Junior Member
Hello everyone on the forum.

Landed into a difficult spot with my home computer setup with LAN. Recently I had an issue that was resolved with replacing the RAM. When I connected the laptop to the network, I felt a mild electric shock. After disconnecting ac power, with the LAN cable connected, I checked with a voltage tester screwdriver on the metal body of the laptop and lo behold, the lamp was glowing. I didn't want to risk damaging the laptop so removed it and tried to trace the fault right up to the two main sources, i.e. the ac power supply and the internet router (extender).

I didn't find any problem with the ac source, having confirmed with a digital multimeter the L-N and L-E voltages as almost equal (1 or 2 V diff).

I then used the voltage tester screwdriver to check for live ac voltage on the metal shielding of the ethernet cable connector, and on the body of my ethernet switch (Linksys SD208 - old stuff), and the lamp glowed in both cases. Using a multimeter, I found voltage of around 65V ac (I am in India, so the house electricity supply is 240V ac) when unconnected, and 150V ac when connected. Strange!

I replaced the adaptor with a similar one but of TP-Link but the observation were the same.

While I am yet to confirm the above observation, I am unable to understand how can the switch which operates on a 12V dc supply, produce 65V or 150V ac and result in leakage current.

Anyone with a background or technical experience in the above area - please help me understand so that I can pinpoint the problem and get to work.

Thanks in advance.
 
Thanks but as I said, "I replaced the adaptor with a similar one but of TP-Link but the observation were the same." That should leave us suspecting the switch rather than the brick, no?
 
ssimlai said:
Thanks but as I said, "I replaced the adaptor with a similar one but of TP-Link but the observation were the same." That should leave us suspecting the switch rather than the brick, no?
Click to expand...

Yes, most likely the switch. I’d swap it out asap. Seems like you know the answer tho 😉
 
Replacing it was easy but the intent behind my post is to ask if an expert knows how and what led to the device developing spurious AC voltage. As the forum is named AnandTECH I believed some technical expertise would be there to fall back upon.
 
ssimlai said:
Replacing it was easy but the intent behind my post is to ask if an expert knows how and what led to the device developing spurious AC voltage. As the forum is named AnandTECH I believed some technical expertise would be there to fall back upon.
Click to expand...

If it started out of nowhere, an internal component likely failed and allowed voltage to get to the points that you tested against. Which internal component? Open it up and take a look!
 
Have you tried plugging the switch into a different outlet, preferably on a different circuit and observe the same behavior? Any other devices plugged into that same outlet where the switch is located?
 
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