John Robertson wrote in message
...
N_Cook wrote:
How much is down to conflict between power supply designer and EMC
compliance bod?
Designer: I want convection vent holes here, here and here, through the
shielding
EMC bod: No way, I can let you have a few holes here and thats your lot

Just repaired an LCD monitor, probably started failure with ESR'd caps
then
ohmic zener and eventually blown backlight inverter pair of transistors
and
blown fuse. Plenty of holes top, side and bottom of the shield on the
digital processing side but only holes at the top on the ps side. So air
comes in on the colder side at bottom rises to the top by about mid
board
and little or no air traversing the hottest section, that whole section
in a
dead-zone in more ways than one, brilliant



Any cap with shrinking plastic film is ready to be replaced. Figure out
what circuit it is in and find either a low ESR or low Inductance (or
both) cap to replace the poorer original one.

We put fans on any LCD screens that we install in any sort of cabinet.

It would be nice if tiny fans were installed by the manufacturers...

John :-#(#

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They would not have to be high revs, just enough to circulate air in or out
of dead zones like between heatsink plates. In this case the hottest as
evidenced by the shrunk sleeves , were from between a U of heatsinkery. I
will try controlled heating of one of the other removed caps of the same
make to see what temp it must reach to axially shrink the wrappers.
Do they make miniature
longitudinal fans say .5 inch diameter x 1 or more inches long ? Failing
that it would be some ducting associated with standard 1 inch fans.

If no fans allowed I would have placed the ps board over the "scaler" board,
assuming the whole monitor is not used horizontally