[HBR] Using vintage Carbon Comp resistors

[banfig]

Hi,

there was an article in the March/April QEX about the topic with data 
and analysis.
The title is  "Carbon Composition, Carbon Film and Metal Oxide File 
Resistors" By K8ZOA.


73
Gabor KD5PGI

Hopperdhh at aol.com wrote:
> Don and Marvin,
>
> I had heard  that carbon resistors increase in value due to very small 
> fractures in the  carbon that propagate.  I can see how this would cause the 
> resistance to  increase.  Perhaps moisture in the cracks keep the carbon molecules 
> from  touching each other which would make a higher resistance path.  Maybe it 
> is  a combination of cracking and moisture.
>
> I do know that even unused carbon  resistors increase in value over time.  
> Also, it has been my experience  that high value (100's of K ohms or megohms) 
> tend to be the worst offenders --  sometimes being 2 or 3 times their original 
> value.
>
> Dan K9WEK  
>
> **************Feeling the pinch at the grocery store?  Make dinner for $10 or 
> less. (http://food.aol.com/frugal-feasts?ncid=emlcntusfood00000001)
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