Date: Mon, 30 Jul 2012 12:56:56 +0930
From: "Leigh Turner" <invertech@frontierisp.net.au>
Subject: Re: [Amps] Dedicated RF / tube query
Hi Dan,
Not that it matters much, but are you absolutely certain that the current
3CX800/3CPX800A7 tube products sourced from CPI are not of Chinese origin
and instead supplied to CPI under an OEM outsourcing supply agreement with
bespoke Eimac labelling / badging done by the China tube factory?
Also I'm curious about the rationale for using two little puppies in
parallel instead of a single 3CX1500A7/8877 tube...it sounds like you have
given this key decision a lot of thought?
Leigh
VK5KLT
## Point well taken Leigh. A single chinese 8877 would make more sense...and
far less expensive
than a pair of Eimac 3CPX-800A7’s. You don’t put 2 engines under the hood
of your truck,
you put one big mother in there.
## 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.
20 kV (working limit) / 28 kV (test limit) vacuum capS
Custom-built edge-wound tank roller inductor (1/16" x 3/8" silver plated
Beryllium)
Toroidal HV transformer with 97% efficiency + or -
Remote display head
etc, etc
## 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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