18 Jul
2010
18 Jul
'10
3:28 p.m.
On Sun, 2010-07-18 at 14:37 +0200, Jörn Nettingsmeier wrote:
On 07/17/2010 10:46 PM, fons(a)kokkinizita.net wrote:
Just for fun I used the German Google to search for the switch issue. It
seems to be something that happens very often :D. Wow, my PC case is
that old, that I had to manipulate the LED jacks, because they don't fit
to modern mobos, but the switches never were broken.
What's a good value for a capacitor?
Btw. I pushed the momentary switch while running a GNOME session on Suse
11.2. As expected the ShutDown-Restart-Suspend-Hibernate menu appeared.
I closed the menu and pushed the momentary switch again, but the the
computer turned off, without doing a shutdown.
What I don't understand is how the contacts
got so dirty.
If a resistance of a few kOhm is enough to make it look
as a closed contact then it can't be handling large currents,
so there should not be any arcing. And the construction of
the thing is such that it is virtually closed, no dust or
whatever could ever creep in.
it can't be totally sealed, as that would require an expensive gasket.
my guess is that the way servers are designed, air is drawn in through
the front (the "cold aisle" in datacenter lore), and expelled through
the rear (the "hot aisle"). after some years of use, it's not so
unlikely for gunk to accumulate pretty much anywhere in the path of the
airflow.
and the conductivity of pure industry-strength gunk should never be
underestimated.
btw, if the bios does not allow the boards to be configured as "always
on after power loss" (common on older hardware), a capacitor in place of
the momentary power switch works nicely, provided its charging current
has dropped to zero before the bios thinks it's a
more-than-four-seconds-turn-me-off event.