Yes, you MUST pass air through the socket to cool the seals whenever heater
voltage is applied!
Vic k2vco/4x6gp
Sent from my phone
> On Nov 28, 2014, at 5:43 PM, Pete N4KW <n4kwpete@centurylink.net> wrote:
>
> 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@outlook.com>
>> To: "Amps group" <amps@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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>
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