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

To: "Fuqua, Bill L" <>, Peter Voelpel <>, "" <>
Subject: Re: [Amps] Power from Pair of Eimac 4 x 150 a / 7034?
From: Colin Lamb <>
Date: Sun, 28 Dec 2014 13:53:00 -0800
List-post: <">>
Collins Radio changed the output tubes in the KWS-1 from the 4X150 to the 4X250B and there were enough differences that a service bulletin was required. They noted that the input capacitance decreased when the ceramic 4X250B came out (which I believe was then called 4CX250B). I think it was either SB 5 or SB 6 for the KWS-1. The Service Bulletin mentions 4X150 (not the A) and notes that there were both glass and ceramic 4X250B tubes, with different input capacitance.

73,  Colin  K7FM

On 12/28/2014 1:34 PM, Fuqua, Bill L wrote:
   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 

73,  Colin  K7FM
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