--- Jack Smith <[EMAIL PROTECTED]> wrote:
> Unlike fine wine, carbon composition resistors do not get better with age.
Yea verily!
I have observed effect myself with quite a number of 1/4-watt 5% tolerance
resistors that have never been used, are probably at least 20 years old, and
have been stored at room temperature.
In particular, a collection of 75 ohm resistors read extremely high -- in some
cases nearly DOUBLE their rated value!
I have not seen this effect as much with carbon film resistors of similar
value, vintage, tolerance, and power rating.
I made this discovery almost by mistake about two years ago. I had been using
the 75-ohm resistors as terminators in NTSC analog video circuits for quite a
number of years. While these circuits worked fine when tested on the bench
using a video test pattern generator (that had been previously calibrated using
one of these problem resistors as a terminator), improper video levels were
experienced when these circuits were used outside the test environment.
73, de John, KD2BD
Visit John on the Web at:
http://kd2bd.ham.org/
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