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Re: [Amps] Item # 170692212503

To: Sam Carpenter <>
Subject: Re: [Amps] Item # 170692212503
From: "Roger (sub1)" <>
Date: Sun, 11 Sep 2011 18:51:03 -0400
List-post: <">>
On 9/8/2011 10:01 AM, Sam Carpenter wrote:
> 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.

I dropped him a note via e-bay and he ignored it so I'm pretty sure he 
knows the tube is made of unobtanium.
I'd be glad to give him half the price and then rebuild it, but 
certainly not as a collectors item.  Other than the socket and filament 
transformer it'd be a relatively easy conversion to either the 4CX1500B 
like the current production model or the much less expensive Chinese 
FU728F which I think  is capable of about 60% more output or 2.5KW PEP 
pr 2 KW nominal.

Seems like I had one on order, or was in the process of ordering one 
when production stopped on the 4CX1600B.  That was a while back.  One of 
the dangers of ham equipment that is produced in small lots. Parts can 
go obsolete and we just don't produce much demand.


Roger (K8RI)
> -----Original Message-----
> From: [] On
> Behalf Of Roger (sub1)
> Sent: Thursday, September 08, 2011 2:11 AM
> To:
> 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
> 73
> Roger (K8RI)
>> 73
>> Roger (K8RI)
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