Hi,

to be on the sure side, it is a worth of effort to replace resistors with 
same value/power rating and check temperature by IR meter if available. I 
am 50 and I wonder the decreasing size of the same-rated resistors, which 
seems to me as somewhat misterious (or people tends to gamble).

Regards,
Imre

On Thu, 6 Apr 2006, Dwayne Reid wrote:

> At 02:52 PM 4/6/2006, Wouter van Ooijen wrote:
>> I customer returned a motor controller to me. It contained two parallel
>> 1 Ohm carbon resistors, which both had failed open. Nothing to be seen
>> on the outside, just infinite (> 5 MOhm) and high (~ 500kOhm)
>> resistance. Is this a known failure mode? Possible causes?
>
> Seen if often.  Metal film and carbon film both have lousy peak power
> ratings.  I tend to use wire-wound or metal oxide resistors in those
> applications.
>
> Watch out for just which metal oxide resistors you get.  The ones I
> have had the best luck with have a continuous film over the entire
> surface of the resistor.  Those with a spiral cut do not have as good
> a peak power rating as those without.
>
> dwayne
>
> -- 
> Dwayne Reid   <dwayner@planet.eon.net>
> Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
> (780) 489-3199 voice          (780) 487-6397 fax
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