[Amps] 4CX1500B's -- worth using?

[Carl]

The 4CX1500B is a direct replacement in a Collins 30S1 without any changes 
OR the increased screen voltage mod can be done for more power. Idle current 
bias needs a tweak and a heat extractor is a good idea if its used heavy 
duty. The nominal filament current is 1A more.

A friend had a pair on 2M that would do over 3000W for EME and contests.

Not to be confused with a 4CX1500A which has a real grid and can be well 
abused without damage.

Carl
KM1H


----- Original Message ----- 
From: "David Kirkby" <david.kirkby at onetel.net>
To: <dhallam at knology.net>
Cc: "Vic K2VCO" <k2vco.vic at gmail.com>; "Amps reflector" 
<amps at contesting.com>
Sent: Wednesday, June 20, 2012 3:52 PM
Subject: Re: [Amps] 4CX1500B's -- worth using?


On 20 June 2012 20:37, David C. Hallam <dhallam at knology.net> wrote:
> That's what I was trying to imply. The writer of the original post on the
> matter seemed to have the idea that a 4CX1500B was not as good as a
> 4CX1000A.
>
> David
> KW4DH

I don't think they are direct replacements. IIRC the screen voltage is
different, though perhaps not so drastically so that your could not
use the same screen voltage. The filament of the 4CX1500B needs more
current than that of the 4CX1000A if I recall correctly.  The 4CX1500B
will produce a cleaner signal.

I built a twin 4CX1000A amp for 2m, and never did get it working very
well. I recall speaking to John G4FRX (now GW4FRX) and he said the
4CX1000A caused more problems for hams than any other tube. I don't
think its considered one of Eimacs best tubes. The 4CX1500B is
certainly superior.

As I say, there are date sheets on my web site.

dave
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