----- Original Message -----
From: "Sam Carpenter" <sam@owenscommunication.com>
To: "'Rob Atkinson'" <ranchorobbo@gmail.com>; <amps@contesting.com>
Sent: Wednesday, July 20, 2011 11:41 AM
Subject: Re: [Amps] Supply question
> When you run the 3-500 easy, you will have a greater chance of arcs than
> if
> you run the cherry red or orange. The gettering material is on the anode
> and
> it requires color, sometimes significant color, to eat up the full range
> of
> gas. I would venture to say that you may have less chance of arcing in a
> higher voltage amp that is used regularly.
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Rob Atkinson
> Sent: Wednesday, July 20, 2011 11:16 AM
> To: amps@contesting.com
> Subject: Re: [Amps] Supply question
>
> I understand that with 3-500 the 3rd order IMD gets pretty lousy when
> the Ep gets up there much above 3 KV.
Read the spec sheet.
>
> I also had some idea you get a much bigger chance of arcs in the tube
> if you push the Ep way up there near the limit.
Very true when gas is involved as the voltage needed to ignite is in inverse
proportion. A 4000V amp still outgasses when not regularly used and is more
prone to arc when turned on.
OTOH Chinese tubes may not even hi-pot at 7000V which is why Ameritron
rejects so many since they could arc on a normal voice peak. I believe they
test to 9 or 10KV. Even a little bit of gas will ignite an arc when the
threshold is low.
A good Eimac used to hi pot above 12KV when new since they were rated for
Class C AM at 3KV.
Personally I would never run any unknown tube without a hi pot first and if
necessary a full gettering at around 1000V
Carl
KM1H
.>
> comments?
>
> 73
>
> Rob
> K5UJ
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