----- Original Message -----
From: "Roger (sub1)" <email@example.com>
To: "Sam Carpenter" <firstname.lastname@example.org>
Sent: Friday, September 09, 2011 9:54 PM
Subject: Re: [Amps] Item # 170692212503
> On 9/8/2011 10:01 AM, Sam Carpenter wrote:
>> These are two totally different amps. The one with the 4cx1500b is new
>> is basically the Eimac type 4cx1000 with more dissipation. The older
>> 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
>> for the American market.
> Although a good many tubes get over rated when I look at the 4CX-1600B
> the anode doesn't look anywhere near capable of the dissipation of the
> GU-84B (4CX2500). How much emission it had, I don't know. For example
> the 4CX1500B doesn't have a lot of excess emission, yet it has a 1500
> watt anode. I don't think, but don't know for sure Carl probably does)
> that running a 4CX1500B in AB1 or 2 you couldn't even reach the tubes
> rated dissipation. OTOH the Chinese FU728F which has a slightly larger
> anode than the 4CX1500B (1/2" taller but is the electrical equivalent )
> only is rated at 1200 watts dissipation, BUT it will easily run 2KW
> nominal, or 2500 watts PEP output. 2 KW nominal at 60% would use the
> 1200 watts nominal and it has the emission to run 2.5KW PE
> I have heard the renumbered 4CX800s only have a 600 watt anode, but
> that's still plenty for running the legal limit. OTOH if you want to
> run the legal limit class A you are going to need some serious tubes
> with at least 3 KW anode dissipation.
> Tubes that will work in legal limit amps are fast becoming expensive.
> Roger (K8RI)
The 4CX1600B is a GU-71B and the Pd varies from 1500-1600W depending on the
Russian document you read.
Yes, the GU-74B is rated at 600W even in SSB service so its no surprise they
run out of emission early when hams "innocently" push them past 1500W to the
2200-2400W thats possible due to the above spec HV. Customers who bought
into that farce/fraud got snookered.
The 4CX1500B is another joke thought up by Eimac marketing, it should have
been a 4CX1000B or something similar that had some reality. The 4CW2000A is
a water cooled 4CX1000A with a 2000W Pd yet its absolute maximums are 3000V
and 1A. It makes you wonder what the Pd of the air cooled versions really
is. More marketing crap.
Does an 8877 really have a 1500W Pd? Look at the 3CX1000A7, a very rugged
tube with a ridiculously expensive socket similar to the 4CX1000A. Rated at
1000W Pd with a cooler identical to the 8877. In 1975 it received a new
1500W SSB rating so they could sucker Alpha into buying a tube that had a
very limited market. Thus the Alpha 70 was born and wonder of wonders after
Eimac milked that they released the 8877.
And you wonder why Im cynical.
A pair of 3-500's at 3000V will run 1500W, the AL-82 runs 3200V. Now all the
manufacturs have to do is include some basic fault circuitry to protect
things when they arc. But that wouldnt do Eimac any good for selling
overpriced ceramic tubes that often seem less reliable than the Chinese.
Did I say Im cynical?
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