Hi Gents,
Thanks for the list of various compelling
tubes. Its very nice to see the list for the next HPA
project.
Now, may I ask you one question?
Do you think direct heat tubes such as
those noted as "Instant on /w a soft start required"
will provide really the instant start capability?
As one of six-meter DXers I am also using
a direct heat tube in my HB HPA for a 'scramble
start' with 5 seconds of filament step-start.
But some authorities say one should wait until
the entire tube being warmed up to avoid a
mechanical stress caused by partial heat;
larger the tube, longer the warm-up time;
Actually I can not find the term 'warm up time'
on a spec sheet of these tubes - is it mean
no warm-up time required?
de Han JE1BMJ
----- Original Message -----
From: "Roger" <sub1@rogerhalstead.com>
To: <amps@contesting.com>
Sent: Sunday, August 29, 2010 12:46 PM
Subject: Re: [Amps] Fiament watts
>
>
> On 8/28/2010 10:10 PM, donroden@hiwaay.net wrote:
> > Which of the 3K / 5K tubes have the LEAST filament watts ?
> Figures are taken from Eimac data sheets. There are quite a few tubes
> in the 3000 to 5000 watt dissipation range but I believe these are the
> most popular and common.
>
> 3CX5000A7 10.0V @17.5A 175 Watts Oxide Coated Unipotential (5 min
> warm up)
> YC156 15V @ 15A 225 Watts Oxide Coated
> Unipotential (6 min warm up)
> 4CX3000A7 9.0V @ 41.5A 373.5 Watts Thoriated Tungsten (Instant on
> but need soft start on filament)
> 3CX3000A7 7.5V @ 51.5A 386.5 Watts Thoriated Tungsten (Instant on
> but need soft start on filament)
> 4CX5000A 7.5V @ 75A 562.5 Watts Thoriated Tungsten (Instant on
> but need soft start on filament)
> 4CX5000R 7.5V @ 75A 562.5 Watts Thoriated Tungsten (Instant on
> but need soft start on filament)
>
> By comparrison:
> The following tube pairs can run about 4,000 to 4500watts nominal output
> and possibly 5KW PEP compared to a bit over 5 KW nominal for the 3CX
> and 4CX3000 series.
> IIRC all are 3 min warm up.
> A pair of 4CX1500Bs 6.0V @ 20A = 120 Watts (6.0V@10A each)
> Although the FU728F is rated at 1200 watts plate dissipation I've found
> they actually will run a bit more output than the 4CX1500B
> A pair of Chinese FU728Fs 9V @ 17A = 153 Watts (8.5A each)
> NOTE the FU728F is basically interchangeable with the 4CX1500B with the
> exception of the filament voltage and centering pin diameter.
> A pair of 8877s 5.0V @ 20A = 100 Watts (10A each)
> 3CPX1500A7s (same as 8877 but can run more voltage on the plate)
>
>
> > Don WA4NPL
> >
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> >
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