[ltp] Re: pwm controls in /sys

Karsten König linux-thinkpad@linux-thinkpad.org
Sun, 28 Apr 2013 18:47:50 +0200

Am Samstag, 27. April 2013, 22:17:03 schrieb Henrique de Moraes Holschuh:
> On Sat, 27 Apr 2013, Dave Cunningham wrote:
> > Are those RPMs too low?  Does this mean I need a new fan?
> Your thinkpad needs repair, yes.  But it may not need a new fan.  Have you
> cleaned it up yet?  The two common defects that cause this are: (1) dirt,
> and (2) cracked thermal interface.  (2) is far more serious, a recurring
> problem on thinkpads (especially if you ever handle it in any way that
> causes even minute flexes of the mainboard, such as holding it with just one
> hand) and you must repair it as it slowly damages it for good.  OTOH, both
> are relatively simple repairs.
> To repair (2), you need to remove the heatsinks, remove all the old thermal
> compounds, and replace them with an extremely high performance compound
> (Arctic Silver 5 is one I can recommend, but others that are medium to
> high-viscosity, *non* reactive, *non* conductive _and_ as good or better at
> thermal conducitivty will also work).

I can second this. I did this procedure on my T400 which went into themal 
shutdown every time I launched a VM. The procedure is well documented by 
Lenovo and was at least for me a success, the old thermal grease was very dry 
and gone on one corner of the CPU, that corner also was of a different tint, I 
assume to the bad thermal bridge to the fan.

> To repair (1), remove the keyboard and blow the lint away, hold the fan
> stopped while at it as it is not a good idea to spin it at extreme speed,
> and that can easily happen while blowing the lint away with compressed air.