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@contesting.com [amps-bounces@contesting.com] On Behalf Of
rbethman [rbethman@comcast.net]
Sent: Saturday, November 05, 2011 7:08 PM
To: amps@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@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
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