[AMPS] Power Handling of Resistors

[Tom Rauch]

> More data: at DC I've overloaded 2W metal oxide film resistors 10x for a
> whole minute. They ran bright red-hot, with lots of smoke from the paint,
> but when they cooled down they were still within resistance tolerance.
> 
> Carbon film or solid carbon increase in resistance when grossly
> overloaded like that, because the carbon literally burns away.
> 

But first carbon resistors go through a low-resistance cycle. 

As a matter of fact, operating a carbon resistor at near rated 
dissipation for an extended period can result in a drastic reduction 
in resistance.

That's why carbon resistors should NEVER be used for equalizing 
resistors or voltage dropping resistors in critical systems. The 
single largest cause of electrolytic failures in Dentron and Amp 
Supply amplifiers are the 2 watt carbon resistors used as 
equalizers/bleeders.


 
73, Tom W8JI
w8ji@contesting.com

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