[Amps] 3-500Z cool down time

[Catherine James]

Kim,

   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?

73,
Cathy
N5WVR

--------------------------------------------
On Tue, 6/6/17, Kimberly Elmore <cw_de_n5op at sbcglobal.net> 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?
 Kim
 N5OP
 
        From: Catherine James
 <catherine.james at att.net>
  To: Amps group
 <amps at contesting.com> 
  Sent: Tuesday, June 6,
 2017 9:04 AM
  Subject: Re: [Amps]
 3-500Z cool down time
    
 Given
 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).
 
 73,
 Cathy
 N5WVR
 --------------------------------------------
 Kimberly Elmore <cw_de_n5op at sbcglobal.net>
 wrote:
 
  True
 enough; I was simply
 
 statingthat the 3CX1200 is a ceramic replacement for a
 glass
  envelope.
 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
 <dezrat at outlook.com>
   To: Amps group <amps at contesting.com>
  
   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
 
 wrote:
  
  >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. 
 
 >Kim
  N5OP
  
  REPLY:
  
  Yes, but that's a
 very
  expensive tube. I
 was thinking of a ceramic
  3-500Z for the same price as glass. 
  
  For what they are asking
 you
  might as well get
 an 8877. Different
 
 socket
  but lower drive
 and more output.
  
  73, Bill W6WRT
 
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