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Re: [Amps] Series C in amp output

To: "Bill Turner" <>, "Amps group" <>, "Mark, K5AM" <>
Subject: Re: [Amps] Series C in amp output
From: "Carl" <>
Date: Fri, 16 Feb 2018 21:34:21 -0500
List-post: <>
Often tubes can be very long lived as has been reported many times.

A few years ago I had a well used Tempo 2000 (Johnson Thunderbolt II) in for service that still had its original 1962 3-400Z's at full power.

My LK-500ZC was partial payment from Amp Supply for some consulting work; the 1986 3-500Z's are still at full power even after having been beat real hard during decades of contesting, serious DX chasng and as AM linear a good part of the past 10 years. The glass is a bit brown but the tubes were always run in spec.

My 1963 prototype NCL-2000 was converted to 6M in 64 and the defective 8122 RCA tubes (no screen support) were replaced in 67. Those were removed in 2011 only because the output was down to 600W and the IMD was way up. Never abused. The pulls from a distributed amp are an easy 1200W.

I have a DTR-2000L, MLA-2500, and SB-230 with the original tubes since I dont beat the hell out of them.


----- Original Message ----- From: "Mark, K5AM" <>

Bill, the amplifier was built in 1971, and ran with the
first tube for 17 years. That tube still ran perfectly,
but I had a few spares on the shelf, and read
somewhere that it was good to rotate them, for
gettering. So I began to rotate tubes about every five

Very heavy DXing and contest use over 47 years, but
no problems. The 4CX1000A has serious grid and
screen current limitations, but the amp has a full set
of protection circuits.

As for tube life in general, I can relate that the 6
meter amplifier that I built in 1961, with push-pull
Eimac 4-400A tubes, is still running full power after
57 years, with the original tubes, used to work 138
countries on 6 meters. Was Eimac great, or what?
And of course Bill Orr, W6SAI (SK), the Eimac ham
contact at the factory, was great to chat with
whenever I phoned him with a question.

6 meter amp:


Mark, K5AM

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