[Milsurplus] Carbon Comp Resistors: The Darkness Gathers?

[Mark K3MSB]

I've found it's the lower values, typically up to maybe half a meg, that go
high with the lower values, say under 100 ohms, to be particularly prone to
going out of tolerance.

I've about two medium postal boxes of unused carbon comp resistors in the
"pile".    Since I'm pretty color-blind the only way I can determine the
resistance value is to use a meter, and then I'd have little chance of
knowing if it matched the funny colored rings around the body.

73 Mark K3MSB

On Mon, Jul 2, 2018 at 4:15 PM, David Stinson <arc5 at ix.netcom.com> wrote:

> I've always heard that the carbon comp resistors
> that fail Hi-Z most often are those in the
> Mega-Ohm range ("green band").  Oddly, over the
> last four major projects:  TCS, ATD, RAX and now
> SCR-522, haven't found that to be the case.  The
> resistors most often failed-High are in the
> 15K-500K range, with the #1 "bad guy" being 47K
> Ohms, followed by 470K.  I remember changing one
> or two Mega-Ohm value resistor in the last three
> projects.  Every 47K resistor in the last TCS
> receiver and in the ATD had to go.
>
> Which brings me to this:
> I've got piles of NOS Carbon Comps that have been
> following me around for eons.  The majority of
> these have started reading Hi-Z by 5% or more.
> Many by much more.  I just threw a half dozen NOS
> 100K away because they read from 107K- to
> 122K-Ohms.  Other values are showing similar
> drift.
>
> Has twilight come for Carbon Comp resistors?  I've
> stopped buying them at hamfests and use only the
> newer, ceramic looking thingies for projects now.
> What do you think?
>
>
> GL OM ES 73 DE Dave AB5S
>
>
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