[Boatanchors] [Milsurplus] Carbon Comp Resistors: The Darkness Gathers?

[howard holden]

I recently went on a recapping n resistor check/replace binge, on an SX111, SX101A, NC125, Howard 435, and a Viking Invader. The Hallis and the invader were all good on the resistors, the NC and the 435 each had near a dozen each out of tolerance. Maybe it's age related. The NC and 435 are 1-2 decades older than the others.  

I've also got a zillion NOS 1/4 watt carbon comps (at least they look like comps) mainly high value and haven't found a bad one yet from them. 

Howie WB2AWQ

Sent from my iPhone

> On Jul 2, 2018, at 13:19, Peter Gottlieb <kb2vtl at gmail.com> wrote:
> 
> I’ve gone through my old resistors and had to discard most of them due to all being out of tolerance high. I have gone to properly rated carbon or metal film ones for repairs. 
> 
> 
> Peter
> 
>> On 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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