If so, then the designer of the board was an incompetent fool, and
should be fired or at least given some extra training. Power resistors
need to be derated or specially mounted to keep them from burning the
board. A 10 watt resistor cannot dissipate 10 watts when mounted on a pc
board. Sheesh.
Think single-side/no layer PC boards from the 60's thru the early 80's..
I take it that you haven't dealt with stuff that's 15-20 years past it's
own design life? It's not really an excuse for the original designer,
but that's the reality of where much of the critical stuff is at today.
In the above, it's often that the "burner board" was installed in a
"control cabinet" that was 90+% "empty space". There was no
airflow/cooling issues then. That same "control cabinet" has been
stuffed to the gills with added gear until there was not enough airflow
to stop the burn.
I'm sharing some of the guilt on that, guess who put all the extra crap
in? (Usually under protest). If you can't get the real estate, you do
this crap.
I've seen some of those boards in "updated versions", the fix was to cut
a window in the board underneath where the burns occurred. Crude, but it
works.
But in the end run, those burns seldom resulted in a true fail. All we
did was carve out the burn with a knife if we could swap it out or take
it off-line, and that was mainly for looks.
--
"Shit this is it, all the pieces do fit.
We're like that crazy old man jumping
out of the alleyway with a baseball bat,
saying, "Remember me motherfucker?"
Jim “Dandy” Mangrum
