Fred said:
> I remain convinced, however, that a carbon composition resistor will
>change in value over time even if it is not heated.
Having inherited my fathers junk box, as well as having built up mine over the
last 40 years, I too have a number of brand new, never used carbon composition
resistors. Measurements indicate exactly the same thing that Fred found - they
have gone high. I have some 'High Stability' carbon comp resistors that are over
40 years old, and have been used; they're still within the tolerance rating. I
even found a few ordinary carbon comps which were still in their 1970's military
packaging, and they'd gone high, too.
It appears that 'ordinary' carbon comps drift high. 'High Stability' ones seem
OK - they have a pink band on them as well as the normal colour code for value
and tolerance. But I've never seen any 2 or 5 watt high stability ones.
Now I also have from father's junk box some 5 watt solid carbons that are about
2 inches long and 5/8 inch in diameter, dating back to WW2. They are still in
tolerance............
I ought to check some of the carbon film ones I have - I know some of them have
never been used, and are 30 years old.
73
Peter G3RZP
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