[Amps] Holding a vacuum

[Alek Petkovic]

Yes. That's correct.

I use a cheap plastic tub with a filament transformer and small blower 
from an old microwave oven mounted inside. The tub is inverted and the 
base of the tub has the tube socket and tube mounted on it.

The lid of the tub forms the base. I can lift the tub off the base and 
shoot up inside, at the bottom of the tube, with a infra red thermometer 
(cheap Chinese copy of a Fluke, that is surprisingly accurate) to keep a 
check on the temperature/s.

I have found that this set up is sufficient, even for tubes as large as 
the YC156.

I did GU74Bs, FU728Fs, GU84Bs and YC156s. I just changed out the 
filament transformer each time and enlarged the hole to accommodate the 
larger socket for each tube type. When the dozen or so tubes were all 
done, the plastic tub was thrown in the recycle garbage bin.

The next time I did it, I bought another tub and did the same thing, 
progressing from the smallest to the largest tube sockets. It takes less 
than 10 minutes to chnge to a different tube type.

73, Alek
VK6APK










On 29/11/2014 12:39 AM, Carl wrote:
> A small fan is fine.
>
> Carl
> KM1H
>
>
>
> ----- Original Message ----- From: "Pete N4KW" <n4kwpete at centurylink.net>
> To: <amps at contesting.com>
> Sent: Friday, November 28, 2014 10:43 AM
> Subject: Re: [Amps] Holding a vacuum
>
>
>> Earlier this week I emailed Eimac with the question about shelf life 
>> of the new 4CX1500B tubes that I have.  I also asked about the serial 
>> number on the tubes and how to read it.
>> I am awaiting the code for the serial number, regarding shelf life 
>> they recommended that I at least apply filament voltage every six 
>> months.  If one was to apply filament voltage would a blower be 
>> required or not for this tube.
>> 73 Pete N4KW
>>
>>
>> On 11/27/2014 3:24 PM, Carl wrote:
>>>
>>> ----- Original Message ----- From: "Bill Turner" <dezrat at outlook.com>
>>> To: "Amps group" <amps at contesting.com>
>>> Sent: Wednesday, November 26, 2014 11:08 AM
>>> Subject: [Amps] Holding a vacuum
>>>
>>>
>>>> I'm curious as to your experiences with tubes in long term storage.
>>>> The question is, which type holds a vacuum better - glass or ceramic,
>>>> or is there no difference?
>>>>
>>>> My own limited experience says ceramic is better, but that is only
>>>> with a few tubes.
>>>>
>>>> All comments welcome.
>>>>
>>>> 73, Bill W6WRT
>>>>
>>>
>>> "It all depends" as they say.
>>>
>>> Some ceramic/metal and glass/metal are notorious leakers such as the 
>>> 4CX300A and PL-172 and PL-172A. Popular ones such as the 4CX150A 
>>> family, 8874 family, 8877, 3CX3000A, 4CX1000A/1500B hold vacuum well 
>>> but the indirect heated types such as the ones above (not the 3X3) 
>>> should be run up to 24 hours with just filaments to regetter from 
>>> outgassing. This includes the 8072/8121/8122 and long stored Russian.
>>>
>>> Eimac had a couple of  bad years in the late 80's with the 3-500Z 
>>> when they moved the plant to SLC; other than that they just had 
>>> outgassing as did most glass tube and need regular running with 
>>> color to regetter.
>>>
>>> The 3-1000Z and 4-1000A often went to air as well as did many of the 
>>> larger WW2 tubes such as 450/750 TH/TL, 6C21, and larger.
>>>
>>> OTOH I have a pair of 1934-35 HK-354's that still run at a KW on AM 
>>> but other 20's to 30's TX tubes are almost impossible to find 
>>> (mostly RCA) with seals intact; 203A, 204A, 211, 849, 851, 852, and 
>>> others.
>>>
>>> Ive little to no experience with Russian and non US clone Chinese 
>>> tubes but have heard a lot of good things about Chinese 
>>> military/broadcasting ones in particular.
>>>
>>> Carl
>>> KM1H
>>>
>>>
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>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>
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