Hi Carl,
Repeated reference has been made on this reflector regarding so-called
"...medical pull" tubes...
How does one go about getting one's hot little pinkies wrapped around one of
these rascals...? Where do you go, who do you ask, & who might you have to
"whack"(!) to get one, or more...?
~73~ Eddy VE3CUI - VE3XZ
*******************************************
----- Original Message -----
From: "Carl" <km1h@jeremy.mv.com>
To: "Roger (K8RI)" <sub1@rogerhalstead.com>
Cc: "Amps" <amps@contesting.com>
Sent: Saturday, July 26, 2008 10:47 PM
Subject: Re: [Amps] Building an Amp, Selecting a Tube
> Any 3CXPX1500A7 or Y-xxx medical pull at close to full output. Reasonably
> priced so you can buy a spare or two.
>
> At your criteria I cant see any other tube that comes close that will
still
> be around 10 years down the road (my prediction) and is affordable,
reliable
> and an easy build.
>
> Id rather build a no compromise MF-HF amp that covers (or makes expansion
> provision) all current and potential new bands (600 and 60M) and leave 6
to
> a monobander or 6 & 2.
>
> Carl
> KM1H
>
> ----- Original Message -----
> From: "Roger (K8RI)" <sub1@rogerhalstead.com>
> Cc: "Amps" <amps@contesting.com>
> Sent: Saturday, July 26, 2008 10:20 PM
> Subject: [Amps] Building an Amp, Selecting a Tube
>
>
> > I've looked over the present offerings for tubes (either one or two in
> > parallel) to comfortably run the legal limit.
> > There are a number of "out of production" Russian tubes that look
> > attractive and are very inexpensive for a one off project complete with
> > a back up tube although I'd like to keep the drive requirements down.
> > There are also some fairly good tubes still in production that aren't
> > all that cheap but some aren't all that bad. There are also the imports
> > which are basically either Russian or Chinese. Although the history
> > appears kinda poor for the Chinese tubes apparently they are getting
> > better and some have done quite well.
> >
> > Of course there is also the 4 legged fuse approach and they are becoming
> > both more rugged and less expensive, but the designs are not at all as
> > simple as the old tube amps. Plus the protective circuitry can be quite
> > elaborate. OTOH I do like the HL1.5-Kfx I have now. Of course I like
> > my old, manual tune Alpha 76A as well.
> >
> > There is even a 4CX-1600B project available, but as the tubes are no
> > longer manufactured and I doubt there were a great many sold to begin
> > with, I'd want a spare tube. My potential goal is a legal limit,
> > 6-meter amp that could run key down for hours.
> >
> > Near as I can tell (from what I've seen) the 4CX-1000 is probably the
> > most linear tube and it's still being manufactured and the price is "not
> > all that bad" although I'd probably want to use a pair of them which
> > would run about a grand just for the tubes plus their not so inexpensive
> > sockets. Of course there are still both the 3CX and 4CX 800's as well
> > which would cost a bit more for a pair of tubes but a whole lot less for
> > the sockets. Both would easily run the legal limit on 6-meters with a
> > bit of room to spare.
> >
> > Using current production tubes, or those solid state four legged fuses,
> > building a well constructed amp will probably cost as much as going out
> > and purchasing a new amp. I'm fussy so if I do build I expect to have
> > the end result look like a commercial amp including the panel. IF I do
> > go solid state I'll probably use current designs for the protective
> > circuitry and plenty of good rugged transistors for a comfortable
> > margin. Also, liquid cooled heat sinks are fairly simple. However as has
> > been discussed, the delta T between the high power transistors and the
> > heat sink can be a bit on the high side even with the best of heat
> > transfer compounds. Basically I'd want one that could run 2KW out
> > without self destructing to feel comfortable at the legal limit. Having
> > HF through 6-meters would be very nice, but a separate amp for 6 is not
> > out of the question. So I guess that is about as all inclusive as I
> > can get.
> >
> > Any socially acceptable suggestions?
> >
> > 73
> >
> > Roger (K8RI)
> >
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> >
>
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