----- Original Message -----
From: w9gt@comcast.net
To: amps-request@contesting.com
Sent: Monday, June 03, 2002 12:33 PM
Subject: True dissipation rating of GU-74B/4CX800A?
Hello amps enthusiasts,
I am preparing to assemble a home brew amp project using Russian ceramic
GU-74B/4CX800A tubes. I sure would appreciate some experienced input regarding
the dissipation ratings of these tubes in the HF range up to 30 MHz. Why do
many of the Eastern European and Russian vendors (and some data sheets) for
surplus tubes describe them as rated for only 600 watts? The Svetlana data
sheet, however, describes them as being capable of 800 watts. Is there a
difference between newly manufactured tubes and the commonly available military
surplus variety other than the markings and brand name? Or, perhaps are these
military ratings vs. commercial or amateur ratings?
It seems that these tubes ,if in fact they are analogous to 4CX800As, should be
capable of 800 watts of anode dissipation.
It is also interesting to note that one U.S. manufacturer of amplifiers claims
to get over 2500 watts output out of a pair of these tubes. I wonder if they
are using the surplus variety or newly manufactured versions? All of this is
leading to a simple question: Would it be a good idea to run two, or three
tubes in a full legal limit amplifier (1500 watts PEP out) and expect
reasonably long tube life and good performance over all bands? Of course, in
consideration of good engineering practice, cost vs. benefits, and reasonable
efficiency.
Thanks for your input!
73, Jack, W9GT
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