Got alot of carbon resistors that seem to be
very old. They test mostly within tolerence. Is
it senseable to use these?
BOBH_

: Got alot of carbon resistors that seem to be
:very old. They test mostly within tolerence. Is
:it senseable to use these?
: BOBH_
:
:
The answer is probably not.

Most old carbon resistor DRIFT high... new or used.
If the resistor was 20% tolerance and you now see it near the top of that range... it will be continuing to drif and drifting higher and higher so it will soon be out of spec.
Best to toss em and buy new carbon film or metal film resistor.. very cheap and very good.
Why take chances ... even if not critical.. for a few cents.. toss 'em.

Agree with Peter but you mentioned most test within tolerance. Since that's the case you might like to use them to keep older radios original.

Many older carbon resistors go up in resistance especially higher values.

Norm

:: Got alot of carbon resistors that seem to be
::very old. They test mostly within tolerence. Is
::it senseable to use these?
:: BOBH_
::
::
:The answer is probably not.
:
:Most old carbon resistor DRIFT high... new or used.
:If the resistor was 20% tolerance and you now see it near the top of that range... it will be continuing to drif and drifting higher and higher so it will soon be out of spec.
:Best to toss em and buy new carbon film or metal film resistor.. very cheap and very good.
:Why take chances ... even if not critical.. for a few cents.. toss 'em.
:
:

: Got alot of carbon resistors that seem to be
:very old. They test mostly within tolerence. Is
:it senseable to use these?
: BOBH_
:
:
;The old dog bone type resistor with body / end / color dot resistance ID marking are questionable. As for the carbon comp resistors with color bands, I have repaired / rebuilt over 100 tube type radios, several TV sets, and lots of sound and theatrical dimming equipment, and used NOS (and recycled) carbon comp for numerous construction projects, and have NEVER had a problem with the banded carbon comp resistors (except for units that were physically damaged, or which had obviously been overheated). But I HAVE seen numerous problems with bad solder joints, and socket damage where someone has replaced resistors and other components. And carbon or metal film resistors do not have the surge handling capability of carbon comp, and I would not expect a 1/2 watt film resistor to work well with more than 1/4 watt dissipation. If it ain't broke, or isn't likely to break, don't fix it. Ed M

I get military surplus carbon resistors from the early 40's. A hand full for $2.00. the leads need to be cleaned, but other than that they are as good as new.

:: Got alot of carbon resistors
::very old. They test mostly within tolerence.

Thanks all --I have probably several hundred from where I do not know. Just seemed like a waste not
to use. Some of the sets I try to repair do not
have much value but did not want to use if they were
highly unreliable.
:

I suggest you measure the resistor first. Then if it is well within the tolerance.. use it.. sure.. but if it measure high near the end of the tolerance range then toss it.
I submit the following lab-type test info for your consideration:
Go here read this research article :
http://www.cliftonlaboratories.com/carbon_composition_resistors.htm