[AMRadio] 4-400 first made when?

Bill Smith hbco2 at sbcglobal.net
Fri Mar 23 14:23:21 EST 2007

----- Original Message ----- 
From: "John Lawson" <jpl15 at panix.com>
To: <amradio at mailman.qth.net>
Sent: Friday, March 23, 2007 7:16 AM
Subject: [AMRadio] 4-400 first made when?

>    In doing some research - I notice that the 4-400 seems to be a fairly
> late arrival, at least as far as RCA is concerned. It's in none of my
> HB-3s, not in my 1962 TT5, but is in the 1975 TT5 manual.   Since my
> transmitting tube library has this 12-year gap, I'm assuming RCA began to
> produce the device sometime after 1964... does anyone have better info on
> the history and development of this very 'popular' power tube?
>    Thanks in advance for any enlightenment!
> Okay - over and out...
> Cheers
> John
> DM09fg

Hi John,

Eimac, known then as Eitel-McCullough, as well as a number of other tube
manufactures faced a dilemma at the end of WWII.  Millions of tubes had been
manufactured and were glutting the market.  Tube manufactures, who had a
good run during the war, faced a consumer market when the war ended.  With
all the surplus tubes available they had to develop a new market to survive.
That is why (and when) the air-cooled tube family of power tubes was
introduced.  4-65, 4-250, 4-400, 4-1000 were only some of the models of the
new designs.

Unfortunately, some companies, such as Heinz and Kaufman were trapped by
accepting late contracts from the military.  The contracts kept the business
alive for a short time after the war ended, but when the contracts ran out,
H&K found themselves out of the consumer market.   They never could catch


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