[Boatanchors] BA Resistors

[Glenn Little WB4UIV]

I cannot get anyone to confirm it, but my theory is moisture. If you 
go back to what makes up a carbon composition resistor, you will find 
carbon granules and a binder. I think that the binder is clay. When 
the resistor is made, the resistance is determined by the amount of 
carbon granules in the binder and how close the carbon granules are 
together. There is then a covering placed over the compressed carbon 
granules and binder after leads are inserted.

For the military to QA a carbon composition resistor, the resistor 
has to be baked, I will find the reference if anyone really needs it, 
before the resistor is checked for value.

The only reason that I can see to bake the resistor is to drive out 
the moisture.

WE see this in boat anchors where they perform better after a 
prolonged warmup. The warmup not only gets the tubes to temperature, 
but drives moisture out of the other components.

This is from my observations and YMMV.

73
Glenn
WB4UIV







At 05:21 PM 2/4/2008, Mike WE0H wrote:
>Maybe oxygen or carbon dioxide?
>
>Mike
>WE0H
>
>jeremy-ca wrote:
>>I dont know why some brands change value more than others but I 
>>doubt if moisture is the only reason if at all.
>>
>>Perhaps someone knows if the manufacturing process involves patents 
>>regarding the carbon molding. I suspect that a chemical reaction is 
>>a more likely suspect.
>>
>>Carl
>>KM1H
>_______________________________________________