Plugging laptop in kills internet connection

Okay folks, I have a real noggin-scratcher (at least, it makes no sense to me!). I hope you geniuses have a clue!

I have a Sony SZ 7xxx series. It's been out of use for a while, and I recently decided to get it back into service. When I booted it up, then internet at the house went down. The network was still available, but no internet. I rebooted the router/modem (AT&T service, all one unit unfortunately) a few times, with no luck. I turned off the laptop, and soon after, my internet returned. Anyway, after a long diagnostic process, here's the deal:

-The Sony will connect to the internet with no problems IF IT IS ON BATTERY. But 2-3 seconds after plugging in the power, the red lights on the modem start going crazy and the internet goes down. If I unplug the laptop, service returns within a few minutes.
-This happens at my parents house, and at my house (both AT&T).
-I don't understand why it would work fine on battery, but plugging in the laptop kills the modem.

-I re-imaged the computer (was going to anyway), with no luck.
-I don't believe it to be a software issue, because it works fine on battery, and I don't even have to be in the OS, just booting to BIOS kills the modem.
-Wired/wireless has same effect

Any ideas?

 

If it happens in BIOS too there must be a hardware issue of some kind.
I wonder if it's something that would happen anywhere or is just your modem/router vulnerable in some way.
If you have another mini-PCI Express card you can use it in Sony to test what happens. If it's just a card it's an easy and cheap fix- so hopefully it's just it.

 

I don't see how it could be the card. The Sony has a hardware/external switch to disable the wifi chip. Even if the chip is off, the laptop being plugged in still kills the modem.

I have a USB wifi adapter, but that doesn't help me.

 

That's a good mystery- I'll give you that.
Still what if you remove the card?
This switch is not a real switch- if you mask two pint on the card it doesn't work anymore so it's possible that the card is powered regardless of the switch if there was a short-circuit somewhere.

 

I'll try late tomorrow or the day after when I get back home.

Thanks for the help downloads!

 

-Disassembled laptop
-Removed wireless card
-Plugged in and hit power button

-Modem dies before Bios screen even flashes.

Oh well.

 

That is a mystery worthy of Scooby Doo. It's not supposed to be possible.
Only other radio device you might have- that coincidentally is working on the same band Wi-Fi does- is Bluetooth module. Do you have one in your laptop?

 

Go get a different power adapter at a B&M store (so you can return it if it doesn't work).

Is your network based on power line?

 

No, not powerline.

I've pretty much isolated it to the power adapter, as sailerboy suggests. After talking to a good electrical engineering buddy, that is the likely culprit. He explained to me how it could be possible, but my mind doesn't quite comprehend that lingo.

 

That's very interesting- if you replace the PSU and confirm it was the problem please make a post about it.

 

downloads,
got a new power brick in the mail today (cheap $10 ebay actually...), and it works just fine. PSU was the problem.

It blows my mind. Thanks for the help!

 

hehe, keep your old PSU and use it in public as a troll PSU?