Dave,I do agree with most of your dissertation however,I do find running the
heater and re-hi-potting to be beneficial to tube de-gassing...I am telling
you this from practical experiance with building around this tube in a real
ham amplifier..Another good thing to do is to run a gas discharge tube
between cathode and grid,generally a Bourns 500v similar to the gas arc
shunt device found in the Alpha Delta coax switches..Have you built an
amateur amplifier around the YC-156 or is your experiance in the MRI field?
73,Jim..K7RDX..
----- Original Message -----
From: "Dave Haupt" <w8nf@yahoo.com>
To: <amps@contesting.com>
Sent: Wednesday, January 28, 2009 2:31 PM
Subject: [Amps] De-gassing/de-barnacling YC-156 tubes (was Source for
YC-156tubes)
>I visited the Eimac factory in San Carlos circa 1989-1990 for the purpose
>of witnessing the manufacture of the YC-156 tubes, which my employer was
>using in production at that time. If your YC-156 has PEM nuts in the grid
>ring, it was built for us.
>
> IIRC, Eimac's procedure for final de-gas and de-barnacling the tube was to
> immerse it in oil (so it would not arc externally) and run the
> cathode/anode potential up to 20kV with a current-limiting resistor and an
> energy storage capacitor. They ran them this way for some number of days,
> with no heater power.
>
> At the factory, our procedure was to run them in the amp, with heater and
> HV applied, for 72 hours. They'd arc a half dozen times the first day,
> then settle down. Our HVPS had a very fast shut-down but no crowbar.
>
> Were I to do it in the home shack, I'd string up enough resistors to get a
> few Megohms at 100 watts, feed them into a few uF worth of capacitance at
> high enough voltage, and run the whole thing at about 15kV. The Joule
> storage capacity of the caps would ensure that enough energy is
> transferred during an "event" to adsorb the gas into the copper anode (the
> heated copper anode is the getter in the YC-156: no amount of heater
> operation will getter the tube), or melt off the barnacle, whichever
> condition causes the arc. In a used YC-156, it's more likely gas; what we
> witnessed in young tubes was proposed by Eimac to be the barnacle issue
> (aka Rocky Point Effect).
>
> Also, bear in mind that it is not possible to guarantee that a tube won't
> arc, so a responsible amplifier design is one that won't get damaged when
> an arc occurs.
>
> 73,
>
> Dave W8NF
>
>
>
> K7RDX wrote:
>
>>> I have purchased several YC-156A pulls from this vendor and nearly every
>>> one
>>> tested very good. They will exchange if you get a bad tube,however I
>>> suggest
>>> if building from scratch to have your tubes tested..Will save hours of
> frustration when you finially light off the new amp..Remember: Most of the
> pulls offered have been stored for several months (Or years) so de-gassing
> is a good idea before use. I test my tubes filament for rated current
> pull,hi-pot for twice rated dc voltage,and run in a cooled jig with
> filament
>>> voltage for at least 8 hrs and then hi-pot again before testing with hv
>>> in
>>> my amp.It`s a lot of extra work but saves other component failure in the
> event of a flash-over..Zonum Industries will do this procedure for around
> 100 bucks plus shipping. GL,Jim..K7RDX..
>
>
>
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