I have seen some 3-500 tubes affected by long storage and some not.
In 1995 I bought a new matched pair of Eimac 3-500 tubes. The date code on the
tubes is 1994. Once in the early 2000’s I tested these tubes and they were
OK. Pulled them out and placed them back in storage; I was not running an amp
that used them. Fast forward to about 2011 and they were both gassy when put
into an AL-82. Arc city. I don’t know if they can be rehabilitated or not by
bringing up the HV low and slow and biasing them to conduction so the plates
heat up. I have not tried that yet, but plan to do so soon.
On the other hand, I bought an old SB-220 from a CB operator back in the early
1990’s. The Eimac tubes in it have 1973 date codes. This amp was never fired
up from 1996 until it was converted to 6 meters in 2010. These tubes are
fine, and still make 1400W on 6 meters. No arcing at all even when first fired
up.
So, I think it depends on the individual tube.
73 Charlie N8RR
Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
From: Joe<mailto:nss@mwt.net>
Sent: Tuesday, June 6, 2017 11:21 AM
To: Catherine James<mailto:catherine.james@att.net>; Amps
group<mailto:amps@contesting.com>; Kimberly
Elmore<mailto:cw_de_n5op@sbcglobal.net>
Subject: Re: [Amps] 3-500Z cool down time
So this SB-220, that has been sitting since 1993, the tubes are most
likely toast?
Joe WB9SBD
Sig
The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com
On 6/6/2017 10:14 AM, Catherine James wrote:
> 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@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@att.net>
> To: Amps group
> <amps@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@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@outlook.com>
> To: Amps group <amps@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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