[Amps] Gettering 3-500 Tubes

[Glen Zook]

The air doesn't leak through the glass!  The problem with the 3-500Z is the seals around the tube pins.  Tubes with small diameter pins do not usually have this problem and those that are decades old still work fine.  There are a few other tubes that this is a problem.  Fortunately, those types are few in number.
 
Glen, K9STH


Website:  http://k9sth.com


________________________________
From: "Fuqua, Bill L" <wlfuqu00 at uky.edu>
To: "amps at contesting.com" <amps at contesting.com>
Sent: Sunday, November 6, 2011 1:09 AM
Subject: Re: [Amps] Gettering 3-500 Tubes

  I have quite a collection of power tubes. Many built 50 or more years ago. I rarely find 
gassy tubes. I have trouble with the idea that air leaks thru the envelope of glass tubes. 
I suspect that if a small amount of air does get into the vacuum it is from a virtual leak. 
These are due to tiny  gas pockets or bubbles in seals or defects in the internal metal parts.
   I is a common problem in research high vacuum systems. The gas does not come from the outside
thru the glass but from a flaw in the glass or other material that holds a small amount of gas after
the tube is pumped out. 
  If a 60 or 70 yea old  large power tube still has a hard vacuum I think it is unlikely that air is leaking thru
the glass. 
73
Bill wa4lav

________________________________________
From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf Of rbethman [rbethman at comcast.net]
Sent: Saturday, November 05, 2011 7:08 PM
To: amps at contesting.com
Cc: R Johnson
Subject: Re: [Amps] Gettering 3-500 Tubes

I wouldn't be concerned with "Gettering".

*IF* there is air leakage into the tubes, they will show a cloudy gassy
look.

Go ahead and try them as they are after you've gotten the rest sorted out.

*IF* it was me, I'd replace the capacitors in the HV section.  20 years
is a long time, and Heath didn't always use the "High" end parts.

Bob - N0DGN

On 11/4/2011 12:05 AM, R Johnson wrote:
> I have just been given an old SB-220. It has been sitting in an attic for 20+ years.
>
> I have removed the tubes and have been bringing the voltage up slowly
> to reform the filter caps. When I get to 120V in and the caps aren't steaming
> and/or blowing smoke I'll be ready to check it with the tubes installed.
>
> I know that the need 3-500's will need to be "Gettered" to remove any gas diffusion
> thru the metal to glass seals on the tube.
>
> I read a procedure on (probably) on this list on how to do it.
> Now that I need it, I can't find it.
>
> Does anyone remember this thread within the last 3 or 4 months ???
> If not,can any recommend how to cook these tubes in ???
>
> TNX es 73
> Bob, K1VU
>
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>

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