[Amps] 3-500Z cool down time

[Jim W7RY]

Yes. Eimac made graphite 3-500 tubes. The really old ones were graphite. 
I've had some. They are 1960s date codes. Looked like a Chinese/RF parts 
tube.


73
Jim W7RY


-----Original Message----- 
From: Richard Solomon
Sent: Monday, June 05, 2017 10:35 AM
To: Amplifiers
Subject: Re: [Amps] 3-500Z cool down time

IIRC, Eimac never made Graphite 3-500's,
if I am wrong, someone will correct me.

The Graphite Anode, being of larger mass,
and who knows what's in them, may need
those precautions.

Saying that, I converted an old SB-220 to
6 Meters and never followed those precautions,
even though both tubes had Graphite Anodes.

But then, they were older tubes, years older.
With today's tubes ....

73, Dick, W1KSZ

On Mon, Jun 5, 2017 at 8:21 AM, Clark Turner <Clark at clarkturnertuning.com>
wrote:

> RF parts supposedly told a local ham that 3-500Z RF parts tubes need a
> minimum of 30 Full minutes of cool down with the blower on and that they
> also need to warm up.  He insisted they told him this information and said
> that if you do not warm up for 5 to 10 min and cool down for 30, the
> graphite will crack.
>
> 3-500z is an instant on tube and one of its largest advantages. I have
> turned my SB220 on, Made contacts and shut it off for 20 years with Eimac
> tubes.
>
> Do you agree with this information?
>
> C
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