[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: Battery charging problem with connected ethernet

Hi all,

> In case that i have been connected to my intranet over ethernet the
> operation mode changes from AC mode to battery mode. It is not possible to
> work in AC mode with a ethernet connection.

This sounds suspiciously like a problem I had some time ago:


I experienced the same problems as you -- wired ethernet did not work with 
that particular AC adapter plugged on one particular network. If I changed 
power supply, ran off batteries, or went to a different network, the wired 
ethernet was fine.

I never did discover exactly what was going on here, but here are some things 
that might help you that I did find in the course of investigating this 
problem and a number of other laptop power supply-related problems we have 
been having with instrumentation in our labs.

* the power supply in question was a non-genuine one. [0]

* laptop power supplies are pretty ugly in the electronic sense. They produce 
amazing amounts of electrical noise in the 50-100kHz range that ends up 
coming out in all sorts of places where it shouldn't. Non-genuine power 
supplies are worse than genuine power supplies at this at this too. [1]

* even though the power supply may claim to produce a certain voltage and you 
can measure that using a voltmeter, when you look more closely on an 
oscilloscope, they tend have a ~0.5V sawtooth around the nominal voltage 
(this sawtooth is the 100kHz noise)

* the "ground" from the power supply tends to float around a bit so you can 
have a substantial difference between the "ground" of your laptop and 
the "ground" of other powered devices that are plugged into it. This includes 
powered usb devices and network cables.

Whether it was the under-voltage or the noise that stopped my ethernet 
connection I am not sure, but I did find that could work around the problem 
satisfactorily in two ways: 1) I changed the network kit at the other end of 
that ethernet cable (it was a network card at the end of a cross-over cable) 
or 2) I took that power supply elsewhere where I only use a wireless network 
and got a different power supply for that location where I used the wired 

I hope that provides some inspiration to you (and suitable amusement for the 
rest of the list!)


[0] it was purchased from ebay... I should have known better... non-genuine 
power supplies seem to cause many more problems than the save in cost.

[1] Looking at 4 genuine power supplies and 5 non-genuine ones that we had 
available to us, we found significantly more noise coming from the 
non-genuine power supplies to the point where a couple of non-genuine power 
supplies for thinkpads just cannot be used any where near our instruments -- 
don't even plug them into the same wall socket!

Stuart Prescott                 www.nanoNANOnano.net

Reply to: