18 Jul
2010
18 Jul
'10
2:37 p.m.
On 07/17/2010 10:46 PM, fons(a)kokkinizita.net wrote:
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.