DIYbanter - View Single Post - Can resistors cause a short-circuit or change value?

wrote in
oups.com:

James Sweet wrote:
wrote in message
ups.com...
hello..
Can resistors cause a short-circuit?

Particularly in a powersupply?
The reason i ask is that because i'm fixing one. From my thinking
resistors are put in a circuit to give resistance unless they
change?
I have seen resitors blown but thats considered high
resistance(infinit)because the resitor is basically gone and thats
not a short circuit i'm talking about. A short circuit resistor is
where a resitor would let most of the current through hence
creating a short circuit situation is this common or even possible.

Thanks

I've never seen a resistor fail shorted, they always go up in value
or go open completely when they die.

Not necessarily. I've replaced large value (100K 1 or 2 Watt) molded
carbon resistors because they lowered in value, 1 down to 15K. The
resistors were running around 220V so it was only dissipating 1/2 Watt
but needed to be 2 Watts because of the high voltage.
GG

This used to happen very frequently in TEK 520 and 520A vectorscope power
supplies.(drop in value)
The 2W carbon comp resistors would get so hot they would drop off the
PCB,or char it to carbon(or both). 39K was one of the values I remember.

--
Jim Yanik
jyanik
at
kua.net