Re: [OT] Good quality hair dryer needed for Squeeze
* Mark Panen <mark.panen@gmail.com> [121210 22:50]:
...
> Every time I shut down my machine due to a thunderstorm and try to power up
> again after a couple of hours the machine is dead and only he LED on the
> MOBO is on.
...
> The only thing that works is hot air from a hair dryer directed at the MOBO
> to the left side of the CPU after cooler for 30 seconds or so.
I work in an environment characterized by high humidity; with
respect to climate, Houston year-round is a tropical mosquito swamp.
Five to seven years ago, I had a pair of ASUS motherboards, both of
which eventually I scrapped due to a problem of the nature which you
describe. Sometimes the boards would power up; other times they would
not power up. When the boards were returned to the vendor (which is
in a drier climate), the problem disappeared.
It would appear that moisture is condensing on the motherboard -- or
more likely, is being absorbed by the motherboard -- so as to provide
a conductive path between two terminals or component leads. Even a
slight lowering of the resistance of the motherboard substrate can
cause trouble.
Also, if components have been soldered in by hand at some point in the
manufacturing process, check carefully for rosin bridges, which also
can be hygroscopic and conductive, even if perfectly translucent.
Rosin is brittle, and can be removed by scraping with a metal probe.
Be ware of solvents, for some solvents can damage components such as
capacitors.
Application of a non-conductive water barrier to the troublesome
region of the motherboard might solve the problem, if you first get
the board really dry. A silicone spray made to waterproof shoes or fabrics
might work, but only if it dries to a non-conductive state.
To get the board really dry (so that trapped moisture is not released
under the moisture barrier), you could bake the board for a day or two
in a home-brew oven using the hair dryer or an incandescent lamp and a
circulating fan, but then you need to monitor carefully the
temperature so as not to exceed the factory rating for storage
operating temperature. Capacitors in particular can be damaged by
elevated temperature.
Populated circuit boards of the highest quality (such as military
grade) often are protected by a "conformal coating"; this is similar
to the way power transformers are dipped in resin and then baked. And
there are silicone-like "potting" compounds which can be applied, so
that a circuit board and its components appear to be encapsulated in a
block of firm gelatin.
RH
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