[Elecraft] Amplifier Vacuum Tubes

[WILLIS COOKE]

--- "TR, K2/100 S/N 838" <elecraft2 at radions.net>
wrote:

> One good source might be Ameritron.  They are still
> selling 811 
> amplifiers and they could not do so if they didn't
> have working tubes 
> (new) to put in them.  They probably charge more
> than RF Parts 
> because they have to quality check them.  I hate to
> point out, anyone 
> so ignorant  that they are unaware you can buy new
> good tubes, may 
> also be ignorant of how to tune and operate them. 
> Don't overlook the 
> possibility that the guy who started this thread may
> be wrong and RF 
> Parts may be right.
> 
> All my life I've heard guys moan and groan about
> 811A's dying.  I've 
> had the same pair in my little home brew amp for 20
> years and I pump 
> them hard.  450W PEP on 80 meters, 400W CW.  You
> just have to know 
> how to take care of them.
> 
> Having said that, I must admit solid state is the
> future, and when 
> the day comes that I can afford a solid state amp I
> will buy one.
> 
> TR, WB6TMY
> 
> From: "Brett Gazdzinski"
> Subject: [Elecraft] Amplifier Vacuum Tubes
> 
> I would like to point out that there are loads of
> good tubes around,
> many places have a lot of old US tubes, I use some
> 100TH tubes made in the
> 1950's,
> and also have a pile of 811a, 812a, 813,s, 4-125,
> 4-400,etc.
> No I dont want to sell any, but there are loads of
> good tubes around.
> Unless overloaded, most tubes seem to keep working
> for a long time.
> 
> I would not get any tubes from China, Russian tubes
> are sometimes ok,
> and the ones from Eastern Europe seem good, but best
> is old US tubes.
> 
> Brett
I am the guy who started this thread.  I could have
trashed two sets of tubes, but I don't think so.  I
bought a used Hunter Bandit with 4 572Bs in 1976.  The
previous owner told me that the tubes needed
replacement and included a set of unused but new
Cetron 572Bs which I installed on the Hunter Bandit. 
In 1988 the power transformer in the Bandit died and I
started looking for what to do.  I found the Dentron
Clipperton-L with bad tubes for a reasonable price.  I
pulled the Cetron tubes from the Bandit and installed
them in the Clipperton and used them until last summer
when I decided to buy some new tubes in case the
Cetrons were a bit worse for 30 years of use. I talkes
to RF Parts and asked which of the three types of 572b
they carried would be best for my amplifier.  They
recommended their Taylor Brand over the Svetlana and
the unbranded Chinese tubes so that is what I bought. 
One had a bad filament on installation.  I returned
them to RF Parts and they replaced them with an
accusation that I drove them too hard.  I installed
the replacement set and ran them at 1800 volts for two
weeks to prevent flash over.  The first time I
selected the 2400 Volt position one or more of the
tubes flashed and took out my high voltage fuse.  I
ran them through the CQ WW SSB contest at 1800 volts
to give them more time for the getters to clear the
contaminants.  I started the CQ WW CW with 1800 volts
but before the contest was over the emission on the
tubes was so low that I was down to 400 watts out on
80 and 100 watts out on 10 with 2400 volts on the
plates.

I pulled the Taylor set and replaced them with my 30
plus year old Cetrons and the amplifier is performing
well today.  Now you can speculate that I don't know
how to tune an amplifier after owning the same
amplifier with the same tubes for 30 years if you
like.  You can buy your products from RF Parts if you
like.  I hope that you do, you and RF Parts deserve to
do business with each other.

Willis 'Cookie' Cooke 
K5EWJ