[AMPS] 4CX1600A and B

[John T. M. Lyles]

At 11:47 PM -0500 11/29/99, Amps Digest wrote:
>Date: Mon, 29 Nov 1999 08:28:01 -0700
>From: "Richard W. Ehrhorn" <w4eto@rmi.net>
>Subject: RE: [AMPS] 4CX1600B Amplifier in new handbook
>
>Hi Ian & all..
>
>May also be worth mentioning that (I think) the original 
>Svetlana-built Russian military tube was the 4CX1600A, which is 
>similar but not identical to the newer 4CX1600B. My impression is 
>that the "B" version may have been derived specifically for 
>commercial export sales - has a bigger and  more efficient air 
>cooler, greater power rating, and specific applications data for 
>SSB. How much the increased ratings are due to the cooler, possible 
>internal changes (which I doubt), or a less conservative ratings 
>philosophy for ham/export applications is unclear.
>
>Can anyone (Ian?) confirm, clarify, correct or add to the above?


The 4CX1600A is identical to the Russian GU91B tetrode, which can be 
seen in the old Svetlana Blue databook (1991/92). All specs and 
dimensions appear identical. Grid dissipation is rated at 0.1 Watts.

The 4CX1600B is different dimensionally - as others have said. The 
cooler fins appear to be of the pressed and welded radial fin design, 
whereas in the -A they appear to be placed inside of a hoop made of 
copper or nickle. This makes the -A have a smoother plate outer 
diameter than the -B. The pressure drop for air cooling is much less 
in the -B, making for a smaller blower with quieter operation.
 
Also, it is stated that the -B has improved electron ballistics using 
a double-focused electron trap configuration. Also, the cathode has 
alternate vertical emissive and non-emissive areas, in a striped 
configuration. This,along with improved alignment of the grids, 
maintains lowest grid current for highest linearity.

Specifications for the -B do not state the grid dissipation on the 
latest datasheet (7/98), instead stating maximum grid current as 5 
mA. In the initial datasheet (7/95) it was 2 Watts power dissipation.

The 4CX1600B replaces the 4CX1600A in Svetlanas product line, so 
unless you have some -A's to burn up, stick with the 'improved' tubes.

John
K5PRO


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