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Re: [Amps] Dedicated RF / tube query

To: Jim Thomson <jim.thom@telus.net>
Subject: Re: [Amps] Dedicated RF / tube query
From: Dan Simmonds <info@dedicatedrf.com>
Reply-to: info@dedicatedrf.com
Date: Mon, 30 Jul 2012 01:32:06 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Sadly, the vacuum caps are sourced from overseas. Jennings in California 
quoted me $1,100 US apiece for US-made caps, and I politely declined.

The Tune cap is rated at the higher (20 Kv) working voltage, and the 
Load is rated at 10 Kv working voltage. The idea here is to use the same 
vacuum caps in the 3-tube export model, and allow offshore capacitor 
purchases to be made in higher volume. So the 2-tube amp will have much 
the same components as the 3-tube (same 7 amp, 13.5v switching filament 
transformer, same 91 CFM dual blower, etc).

Yes I would go for the 3CX3000A7 in an instant, but the size of the 
chassis at that point would be a real turn-off for a lot of guys. K6AER 
and I already struggling with size & utilizing an over / under design.

Dan


Jim Thomson wrote:
>
> ##  On another note, it chokes me to spend $10K on an amp with AIR variable 
> tune + load caps ! 
> Dunno where Dan is getting his 28 kv rated vac caps  from, but I like em.  
>
>
> ##  Now does  this mean vac tune AND load caps..or just the tune cap. 
> Dunno why you require a 28 kv cap for a rinky dinky  3CPX-800A7 tube.
> Heck, my 15 kv rated vac tune cap is plenty for my 3CX-6000A7. 
> A 5 kv cap is plenty for the vac load cap. 
>
> ##  IMO.... I wouldn’t  go the all the trbl of building an amp with vac 
> tune + load
> caps..then stuff a pair of small tubes into  it.   Why spend $1400.00   on a 
> pair
> of 3CPX-800A7’s.... when you can get a 3CX-3000A7 for less...even an Eimac. 
> The 3CX-3000A7  is the  real deal.   The Eimac version is rebuildable !  That 
> tube has
> a  50 ohm input, instant on, 4 kw CCS anode diss, and a 225 watt grid diss.  
> You can use
> the grid  as a dummy load for your  yaesu 1000-D !   Since the grid is bonded 
> to the chassis,
> the grid diss is actually higher.    A simple fast grid fuse is all the grid 
> protection you require. 
> 50 watts in = 1500w  out.   100w =2500w  150=3500  200 =5200w.   The chinese 
> 3x3 is cheap too. 
>
> ##  at 5200w pep out, the IMD3 is  -59db pep.   What more do you want. 
> Dans idea of a remote control head is slick....  stick the amp in another 
> room, and
> let its blowers make all the racket they want.    Dans  use of a 20 kv cap is 
> great....
> if the tube is a 3CX-20,000A7  with the full 10 kv on it.  
>
> Later...  Jim  VE7RF
>
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