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To: "Hardy Landskov" <>, "Colin Lamb" <>, "Bill Turner" <>, "Amps group" <>
Subject: Re: [Amps] THE SKINNY ON MY AL-82
From: "Carl" <>
Date: Sun, 21 Dec 2014 20:17:09 -0500
List-post: <">>
You havent lived until you find a 47K that became 1-2 Meg which is quite common in many old receivers and sourced at only 200-250VDC as screen droppers.

Over 50+ years of building and servicing tube gear Ive only found a handful that went down in resistance.

I have a conservative 10K of NOS carbon resistors and about half again in used condition going back to the late 20's


----- Original Message ----- From: "Hardy Landskov" <> To: "Colin Lamb" <>; "Bill Turner" <>; "Amps group" <>
Sent: Sunday, December 21, 2014 5:19 PM
Subject: Re: [Amps] THE SKINNY ON MY AL-82

It's been my experience that the 2 watt ones are the worst. I measured 1 meg resistors that have drifted up to 2.5 megs. So, think your high voltage is low and your power supply is going south? Measure the resistors first that feed the voltmeter.
73 N7RT

----- Original Message ----- From: "Colin Lamb" <>
To: "Bill Turner" <>; "Amps group" <>
Sent: Sunday, December 21, 2014 2:46 PM
Subject: Re: [Amps] THE SKINNY ON MY AL-82

Regarding carbon comp resistors:

"Not necessarily. Carbon comp resistors can drift both up and down in
value.  I've been replacing them all my life, trust me on this one.
They are essentially unpredictable."

Many years ago, I tested some 2 watt 250 ohm carbon comp resistors for stability. I heated them up to dissipate 2 watts in open air. After a relatively short period of time (I do not recall the time, but it was a number of minutes), I measured the resistance and it had increased. I thought I could go through a number of cycles and have it stabilize. But, every time I ran it through a cycle, the resistance changed. At first, it went up in resistance. But, soon it started going down. It never was stable. And, each resistor was different.

I have numerous old Allen-Bradley 1/2 watt resistors on the shelf and some are stable, while some are not.

Colin  K7FM
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