Before strapping a grid directly to ground, please measure the grid's
resonant frequency with a dipmeter. After strapping a grid to
ground, please re-measure the resonant frequency and publish the
results on AMPS.
- note - the dipmeter test is easier to perform with 2 of the 3 grid
pins floating and only one grounded.
On Jul 18, 2006, at 7:41 AM, Mike Schatzberg wrote:
> Oh, one last parameter, please allow for the grids to be strapped
> to ground
> also.
>
> Sorry for the omission.
When a tube is tired, would that be called an omission of emission?
>
> Mike
> ----- Original Message -----
> From: "k7rdx" <k7rdx@charter.net>
> To: "Tom W8JI" <w8ji@w8ji.com>; "Amps" <amps@contesting.com>
> Sent: Tuesday, July 18, 2006 10:09 AM
> Subject: Re: [Amps] Life and gain of 3-500Z
>
>
>> The tubes (3-500z`s) were from RF Parts. I replaced (Henry 3K repair
>> job)some low hr Eimacs that one had developed a grid to filament
>> short.
> Gain
>> was compared to a nos pair of Eimac`s.Higher zsac for a given Ep
>> and close
>> to 10% more output for a given value of drive.Jim..
>> ----- Original Message -----
>> From: "Tom W8JI" <w8ji@w8ji.com>
>> To: "k7rdx" <k7rdx@charter.net>; "Amps" <amps@contesting.com>
>> Sent: Tuesday, July 18, 2006 3:14 AM
>> Subject: Life and gain of 3-500Z
>>
>>
>>>> Agreed Tom...My question was why would someone run an amp
>>>> with that value of
>>>> line voltage if he knew the effect it would have on the
>>>> fils.
>>>
>>> The filament life issue is primarily an issue with good
>>> manufacturing quality and steady operation at conservative
>>> values.
>>>
>>> Say you run a tube 24/7/52. In a week you have 168 hours. In
>>> a year 8736 hours. There is no thermal cycling. There is no
>>> time for the pin seals to get moist and oxidize ruining the
>>> glass bond. There are no overtemperature operation or even
>>> operation anywhere close to seal rating. The tube is
>>> constantly being gettered. All we have is the filament
>>> erroding away or losing emission from temperature. Emission
>>> life is critical.
>>>
>>> If we turn the amp on 3 hours a day, transmit 25% of the
>>> time with varying power, let the thing sit for a week
>>> without use once in a while, and occasionally run the seal
>>> temps up to maximum, and use (by force now) poor quality
>>> tubes we have a whole different set of likely failures. The
>>> data points from and important to commercial service do not
>>> apply the same way.
>>>
>>>> I do know for a
>>>> fact that a lot of the Chinese 3-500z tubes have higher
>>>> gain than the older
>>>> Eimacs
>>>
>>> I'm not saying that isn't true, but I never saw that happen
>>> at the transition time when Eimac went out of the glass
>>> power grid business and I started looking at Chinese tubes.
>>> I'm not trying to start another long argumentative thread
>>> like the tube curve thread, but rather to learn something.
>>> How did you measure gain and where did the tubes come from?
>>>
>>> 73 Tom
>>>
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>
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>
R L MEASURES, AG6K. 805-386-3734
r@somis.org
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