[Amps] Item # 170692212503

Sam Carpenter sam at owenscommunication.com
Thu Sep 8 07:01:09 PDT 2011

These are two totally different amps. The one with the 4cx1500b is new and
is basically the Eimac type 4cx1000 with more dissipation. The older 4cx1600
is a Svetlana type (Russian) tube. No interchange except that Svetlana
renamed the tube to sound like an American type (EimacType). I understand
that the tube in russian nomenclature has a 2500-3000w dissipation but if
they said that, they might have had fcc acceptance problems and downrated it
for the American market.

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Roger (sub1)
Sent: Thursday, September 08, 2011 2:11 AM
To: amps at contesting.com
Subject: Re: [Amps] Item # 170692212503

On 9/6/2011 3:02 PM, Roger (sub1) wrote:
> I was reading the description of this Alpha 6-meter amp that claims
> "Robust 4CX1600B (Svetlana GU-91B) which is very affordable and readily
> available."
> ** Has the 4CX1600B gone back into production? It's listed as a GU-91B
> from the company that took over Svetlana but I've not found any source
> for them.

The last 6-meter Alpha I saw advertised (on their site) uses a 
4CX1500B.  I'd think a good replacement might be the Chinese FU728F.  As 
the FU728F has a slightly larger centering pin (bout 0.003") it should 
fit the socket nicely.  The only change needed would be a different 
filament voltage and adjust the bias. It should add a good 30% of 
available overhead.  Only downside I can see is what appears to be a 
rather high infant mortality rate for the FU728F


Roger (K8RI)
> 73
> Roger (K8RI)
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