Re: {Collins} carbon composition resistor sources

If considering stockpiling carbon comps, it's worth noting that carbon comp resistors have a habit of drifting higher in value over the years - even high quality resistors that have never been used. Ever measure a batch of NOS carbon comps? Many are out of tolerance on the high side even though they've never been used. The problem is reported to be that the carbon 'plug' absorbs moisture from the air over time. Although I don't have it handy, there is a mil spec procedure for 'cooking' carbon comp resistors in an oven over a couple day period. It involves different temperature settings for different periods of time. I actually had to go through this on a mil project several years back.

Storing them in vacuum sealed bags might help ... of course it would take a number of years to find out! Recent purchases of new-stock, brand-name carbon comps show them to have an unusually shiny coating. Perhaps the manufacturer has started coating them with varnish or similar material to ward off moisture absorption.

Jay W1VD

----- Original Message ----- From: "Gaylord Hart" <gahart@xxxxxxxxxxxxx>
To: "Collins Listserve" <collins@xxxxxxxxxxxxx>
Sent: Monday, November 25, 2013 1:04 AM
Subject: {Collins} carbon composition resistor sources

I prefer to stockpile components for use in my Collins restorations and other projects. When I discover I need to replace a resistor, I don't like having to order a 50 cent resistor, pay $5 in shipping and handling, and then wait several days for the order to arrive. Also, I'm trying to squirrel away components in anticipation of retirement and before I'm completely broke putting three daughters through college. Since I prefer restoring my Collins gear with original type parts when possible, I'm on a carbon composition resistor stockpiling binge right now.

I've compiled a spreadsheet on carbon composition resistor purchasing sources and would like to make it available to anyone on the list who may wish to have a copy. If you would like a copy of the spreadsheet, please let me know OFF-LIST.

The sheet provides names of several companies that sell carbon comp resistors (Mouser, Allied, JustRadios, Nebraska Surplus Sales, etc.), as well as details on the values they stock, the manufacturers they sell (Ohmite, Kamaya, Xicon, AB, Stackpole, etc.), and pricing for 1/4 to 2W ratings, including volume discounts where available. I've focused primarily on 5% ratings since these work almost anywhere, but there is also some info on 10% as well. I've also included any resistor kits they sell. These kits can offer substantial savings by providing volume pricing for 5-10 pieces each of 30-90 different resistor values. If you like using CC resistors, this spreadsheet may save you considerable time and $ (unless of course you are already a CC resistor expert, which many of you are).

My list is of course not exhaustive, but if you know of other good sources for CC resistors, please let me know.

Gaylord Hart
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