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Re: [Amps] 3-500Z cool down time

To: Amps group <>, Kimberly Elmore <>
Subject: Re: [Amps] 3-500Z cool down time
From: Catherine James <>
Reply-to: Catherine James <>
Date: Tue, 6 Jun 2017 15:14:26 +0000 (UTC)
List-post: <>

   It's generally recognized that glass tubes have poor shelf life due to slow 
leakage.  I have heard many reports of this from people I trust.

   They will last much longer if the plate gets hot at least a few times a year 
so that any leakage can be gettered away.  For tubes in regular use rather than 
on the shelf, it doesn't seem to be a problem, but it makes it difficult to 
stock up with spares.  Many amateur users rotate their shelf stock into the amp 
at least once a year.

  Is the 3-500Z used much outside of ham radio today?  If so, who are the 
primary users?


On Tue, 6/6/17, Kimberly Elmore <> wrote:
 The biggest issue with the 3CX1200 is appears to be that
 it's simply not used in much outiside of ham radio.
 I'm not sure what the original design application was
 intended for, but I'm pretty sure it wasn't just for
 amateur use. 

 As for glass tubes, I know that some are notorious for leaky seals,
 but I thought such was rare. Is it a significant problem with the 3-500Z?
        From: Catherine James
  To: Amps group
  Sent: Tuesday, June 6,
 2017 9:04 AM
  Subject: Re: [Amps]
 3-500Z cool down time
 that ceramic tubes appear to last longer on the shelf with
 less leakage than glass, it's a shame that there
 isn't a ceramic tube in the price/performance range of
 the 3-500Z.  It would be well worth paying, say, 10% more
 for ceramic.  But the actual cost multiplier is much higher
 than that, so glass tubes will continue to rule at the low
 end (i.e., far below legal limit).
 Kimberly Elmore <>
 enough; I was simply
 statingthat the 3CX1200 is a ceramic replacement for a
 It's a fine tube, though it requires a fair
  bit more drive. That is,
 aparently, the price paid for a
  high grid dissipation rating. It's easier to
 drive when
  running 4
 kV B+, though. At that voltage, I never fail to
  acieve full output with a
 100 W rig on any band. 
  Kim N5OP
    From: Bill Turner
   To: Amps group <>
   Sent: Monday, June 5,
 2017 9:32 PM
 Subject: Re: [Amps] 3-500Z cool down time
  ------------ ORIGINAL
  MESSAGE ------------(may
 be snipped)
  On Mon, 5 Jun 2017
 20:48:40 -0500, Kim
  >The 3CX1200 is a
  ceramic version of the
 3-1000Z. I have an amp that uses one
  and it's ready in
 under 10 s. 
  Yes, but that's a
  expensive tube. I
 was thinking of a ceramic
  3-500Z for the same price as glass. 
  For what they are asking
  might as well get
 an 8877. Different
  but lower drive
 and more output.
  73, Bill W6WRT
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