[Milsurplus] Carbon Comp Resistors: The Darkness Gathers?

[Clare Owens]

Hi Dave,

I just tested 26 NOS 100K 1/2 watt carbon comp resistors and found only two
or three below 100K, about 8  that were slightly over 10% above  100K and
one that is 129K.

I know exactly when and where these were made, by the way.  Made by the
Speer Resistor division of Airco in their plant in Bradford, PA during the
winter of 1968.  I was there to get weekend test time on their IBM 1800
computer for the Airco Speer graphite plant in Niagara Falls, NY.  They
made huge batches of resistors, sorted them by value into large tote bins
and only striped them when they received orders.  They were striped then
packed into boxes of several hundred of the same value,  If the box held
500 and there were even 499 loose ones left they went into a 55 gallon drum
as waste.  I was able to un-waste a few handfuls each night. and managed to
get a few unused boxes and the corrugated cardboard strips to hold the
resistors.

So, how's that for making a short story long?

Clare




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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