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Re: [Amps] Power from Pair of Eimac 4 x 150 a / 7034?

To: "Fuqua, Bill L" <>, "Colin Lamb" <>, "Peter Voelpel" <>, <>
Subject: Re: [Amps] Power from Pair of Eimac 4 x 150 a / 7034?
From: "Carl" <>
Date: Sun, 28 Dec 2014 20:27:16 -0500
List-post: <">>
You cant make a valid comparison between 2 tubes that are operating at much different plate and screen voltages.

Negative screen current is a function of voltage and loading and the basic 150A simply did not reach that point. Negative screen current is a factor with many ceramic metal tetrodes, not just the 250 series.

Eimac also stressed that circuit losses were responsible for high 150A drive requirements at 500mc but that actual drive at the grid wasnt appreciably more than at 30mc. Chalk it up to lack of knowledge at those frequencies when most on this forum werent even born yet.


I suspect when EIMAC came out with the 7034 they wanted to suggest that they were a good replacement for the 4X150A. Military particularly wanted to use the same part number when replacing tubes in their radios, and I suspect that EIMAC wanted to not only promote the 7034 they wanted to make one tube type rather than 2. There are subtle differences between the two tubes, besides plate dissipation limit. The characteristic curves for the 4X150A does not show any area where there is a negative flow of screen current, while this is an obvious issue some times with the 7034 and 4CX250B. This could be a problem in some cases when interchanging these tubes. There are other differences, one is that when operating the 7034 at 500MHz it does produce the same output power but requires 1/3 the drive power.
Bill wa4lav

From: Amps [] on behalf of Colin Lamb []
Sent: Sunday, December 28, 2014 8:15 AM
To: Peter Voelpel;
Subject: Re: [Amps] Power from Pair of Eimac 4 x 150 a / 7034?

"The Eimac data sheet does not confirm that

The RCA 4X150A/7034 data does:";

The RCA data sheet refers to a 4X150A only, which is a different tube than the 4X150A/7034.

73,  Colin  K7FM
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