T530 Claims Wrong Powersupply

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T530 Claims Wrong Powersupply

Joerg Bruehe-2
Hi!

Since September 2014, I'm using a T530, running Kubuntu 14.04 LTS on it.
Everything (which I need) is running fine.

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 supply
had a lower wattage than expected, and required that I hit Esc to continue.

I did hit Esc, the machine displayed the grub menu, then booted, and I
could use it without issues.

I later tried to reproduce the issue but failed: The system behaved
normal and did not (yet) show such a message again.

All the time, the power supply was the original one, which had never
shown such an effect before.
The power supply is labeled 20 V, 3.25 A, so it is a 65 W one;
CPU is Intel i5-3230M @ 2.6 GHz, 2 cores + hyperthread;
graphics is the CPU-integrated only ("Core processor Graphics Controller").

Checking Google, this is typically discussed related with a "power
manager" which I assume to be some Windows component. This is definitely
not involved here, the machine is Linux-only. Also, the message appeared
before the grub menu.

Should I be concerned, or just ignore this as a once-only thing?

Regards and thanks for all hints,
Jörg

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Joerg Bruehe  - persoenliche Aeusserung / speaking only for himself
mailto:[hidden email]

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Re: T530 Claims Wrong Powersupply

Henrique de Moraes Holschuh-2
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 supply 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

> Should I be concerned, or just ignore this as a once-only thing?

Unless it was caused by bad contact in the power plug or damage to the
power cord, it means some component has aged enough to get borderline
behavior.  It could be in the main board, or in the power supply.

If you can, use an osciloscope to check the output signal of that power
adapter (for ripples, etc).

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Re: T530 Claims Wrong Powersupply

Bjørn Mork
Henrique de Moraes Holschuh <[hidden email]> 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 supply 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.



Bjørn
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Re: T530 Claims Wrong Powersupply

Bjørn Mork
Bjørn Mork <[hidden email]> writes:

> Henrique de Moraes Holschuh <[hidden email]> 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 supply 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...



Bjørn
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Re: T530 Claims Wrong Powersupply

Bjørn Mork
Bjørn Mork <[hidden email]> writes:

> 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...

Well, I went along and tried. Cut the rectangle connector open and found
a 560 ohm 1/4 watt resistor inside.  Replaced it with a 300 ohm 1/2 watt
resistor, which was the closest to 280 I had.  Wasn't really a problem
fitting the slightly larger resistor.  Just carved out a bit more
plastic from the molded connector housing and glued it back together.

The initial test looked good.  But I don't know for sure before I've
tested it with the power supply I have at work.

It would be nice to be able to read out what kind of power supply the
firmware has detected, instead of guessing based on the power drain.
Anyone know how to read that from the firmware?

Being able to force "rapid charging" off would also be great, if
possible. That would allow the use of a misidentified power supply.


Bjørn
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Re: T530 Claims Wrong Powersupply

Bjørn Mork
Bjørn Mork <[hidden email]> writes:

> The initial test looked good.  But I don't know for sure before I've
> tested it with the power supply I have at work.

Now tested.  With an unmodified dongle and a 65W adapter, I saw

$ while true; do grep . /sys/class/power_supply/BAT0/power_now ; sleep 5; done
48972000
48513000
48671000
48770000
48878000
 ..
50309000
50318000
50345000
50342000
50355000
50363000
0
0


At this point the battery was at about 50% full. Then, after replacing
the dongle with my modified 300 ohm, I got:


45705000
46210000
46449000
46689000
46667000
46734000
46733000
46720000
46636000
46668000
46707000
46722000
46603000
46048000
46111000
46160000
46150000
46266000
46367000
46441000
46453000
46459000
46513000
46546000
46333000
46372000


etc.  So the firmware now limits the power drain at about 46W (probably
excluding some loss), making the 65W power supply survive without
disconnecting. Great!  Thanks for the hint.

I only wish this information was better doumented by the dongle sellers,
preferably with options for the smaller power supplies.  All available
dongles and converter plugs seem to be made for 90W supplies.  I guess
there are limits to what you can expect when spending almost a dollar ;)


Bjørn
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