[ltp] T530 Claims Wrong Powersupply

Bjørn Mork linux-thinkpad@linux-thinkpad.org
Sun, 05 Mar 2017 12:09:08 +0100

Bjørn Mork <bjorn@mork.no> writes:
> Henrique de Moraes Holschuh <hmh@hmh.eng.br> writes:
>> On Tue, 28 Feb 2017, Joerg Bruehe wrote:
>>> This morning, I got a message on booting which I've never seen before:
>>> Before it showed the grub menu, the system claimed that the power suppl=
y had
>>> a lower wattage than expected, and required that I hit Esc to continue.
>> Yeah, it uses an idiotic trick to detect power supply size.
>> http://forum.thinkpads.com/viewtopic.php?t=94554&start=90
> Wow, that's interesting.  I suspect that explains the issues I have with
> a barrel-to-square adapter and an old 65W power supply.  It mostly works
> with my X1 Carbon, but intermittently stops charging in the "middle"
> charge area where the power drain will be highest.  I have never
> understood why, since the original 65W X1 power supply has identical
> specs and looks pretty much the same as the old one, except for the
> connector.  If the X1 detects the old supply as 90W due to a hard coded
> resistance in the barrel-to-square adapter, then I can understand why it
> is failing when attempting to "turbo charge" the X1.
> OK, will have to measure these things some day.

Did that, and can only confirm what others have found before me:
 - original X1 Carbon Gen4 65W power supply: 286 ohms
 - barrel to rectangle dongle: 557 ohms
 - original X301 65W power supply (without dongle): 9.9k ohms

Which of course explains the problems using such a dongle with the X301
power supply: It gives the 65W power supply a 90W signature. Not good.

Now the next question is of course: Where do I get hold of a dongle (or
other type of barrel-to-rectangle adapter) with the appropriate 65W
signature? I guess I could cut one open and convert it myself, but the
result wouldn't look all that good...