[Amps] De-gassing/de-barnacling YC-156 tubes (was Source for YC-156tubes)

[k7rdx]

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 at yahoo.com>
To: <amps at 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..
>
>
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps


--------------------------------------------------------------------------------



No virus found in this incoming message.
Checked by AVG - http://www.avg.com
Version: 8.0.176 / Virus Database: 270.10.15/1921 - Release Date: 1/28/2009 
6:37 AM