>Hi-pot tested my GS-35B and it breaks down at about 5600 volts at the
tube
>plate. I have a 10 Meg resistor in series going to the tester to limit
>current. When it breaks down the voltage goes to a few hundred. The
>current on the micro ammeter pegs the needle, on a 250 microamp meter.
>The
>breakdown is very sudden and sharply defined, almost like a switch has
>been
>thrown. Before breakdown I cannot see any current at all even on a 15
>microamp meter.
>
>Does this sound like the tube is gassy or is it arcing?
Yes and yes. Arcing is the sudden breakdown that can happen when a tub
is gassy. Without the 10M limiting resistor, the current would be much
higher and the voltage drop would probably be even lower.
>I plan to apply
>about 2000 volts and I think I can supply enough current to put about
1200
>watts or so into the tube. I'll let it cook for a good long while and
see
>if the heat helps the situation.
I'm not sure where the getter(s) are on a GS35B, but most likely close
to the cathode which is the hottest part of the tube. I don't believe
there is a getter on the anode because that surface doesn't get very
hot, but if you do arrange for some extra anode dissipation, it will
help to raise the temperature of the whole tube to some extent.
>
>Anyone know what breakdown voltage I should expect. I don't know if a
>5600
>volt breakdown is typical or if there is something wrong with this
tube.
The last one I tested (new from UA4LL) showed no trace of leakage at the
9kV limit of my hi-pot tester.
73 from Ian GM3SEK
>-----Original Message-----
>From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of nemo
>zilch
>Sent: 25 February 2015 20:40
>To: amps@contesting.com
>Subject: [Amps] GS35B Gassy, or Arcing?
>
I
>am planning on using about 3800 volts in the amp I am going to build.
That
>will produce a peak RF voltage of something a little over 7000volts at
the
>plate. This tube cannot be used for that, could only run something
around
> 2500 volts.
>
>Information and suggestions appreciated.
>
>Bob W4AOS
>
>
>--
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