[Amps] 4-250A testing

[la7sl Nils Petter]

He was referring to the sellers own description on how the tube was 
tested...
He asked if this seemed OK. That is how I understand the question.
The answer is : This is definitely not ok !
6.3V 8 amp is way off specs for a 4-250A !
This indicates that the seller has not tested the tube at all,- or it is not 
a 4-250A
My advice : keep away from this seller.
according to the tube specs it should be:

TUBE 4-250A / 5D22 / QB3.5/750GA
Filament Thoriated Tungsten
Voltage 5.0 volts
Current 14.5 amperes
as Carl correctly states...as usual :-)

----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: <TexasRF at aol.com>; <rj3819 at yahoo.com>; <amps at contesting.com>
Sent: Monday, September 27, 2010 10:52 PM
Subject: Re: [Amps] 4-250A testing


> The tube has a 5V @ 14.5A filament so Im not sure what you mean by 6.3V @
> 8A?
>
> The only difference between it and a 4-400 is the added fins on the anode
>
> Carl
> KM1H
>
>
> ----- Original Message ----- 
> From: <TexasRF at aol.com>
> To: <rj3819 at yahoo.com>; <amps at contesting.com>
> Sent: Monday, September 27, 2010 4:32 PM
> Subject: Re: [Amps] 4-250A testing
>
>
>> To test for emission, it would seem that the grid voltage would need to 
>> be
>> zero or even positive to simulate the effect of the peak driving voltage.
>>
>> If the emission is normal this would cause a very high cathode current,
>> maybe too high if left for more than a few milliseconds. So, some kind of
>> pulse  test would be safer and less stressful on the tube.
>>
>> Emission can appear normal until the cathode current reaches a level of
>> saturation. If this happens at a level too low, then we call that weak
>> emission.  A tube characteristic chart will show these currents and can 
>> be
>> used to
>> evaluate  cathode emission.
>>
>> Use of AC on the screen and plate will certainly allow a pulse test of
>> sorts. You might try the test with no grid voltage and see how that 
>> plays.
>> The
>> lower voltage you are using seems a good idea as well.
>>
>> Also, the AC cycle needs to be in the same phase for both the screen and
>> plate. Otherwise peak plate voltage will happen when there is reverse
>> polarity  on the screen and visa versa. High positive screen voltage with
>> no or
>> reverse  plate voltage is not good for the screen as it will try to 
>> accept
>> all
>> of the  electrons emitted from the cathode and that can be a bunch.
>>
>> This is a very interesting subject and I hope you test further and let us
>> know what you discover.
>>
>> 73,
>> Gerald K5GW
>>
>>
>>
>>
>> In a message dated 9/27/2010 3:11:23 P.M. Central Daylight Time,
>> rj3819 at yahoo.com writes:
>>
>> This  tube is on ebay ..
>> Worried about getting an older gassy tube .
>> The  seller states ..
>>
>>
>> This auction is for One 4-250 / 5D22 Transmitting  Tube.  The  labeling 
>> on
>> this
>> tube has been worn other than the  tube number that you  can see in the
>> pics. I
>> am not sure of the  manufacturer, but I am quite  sure that it is either
>> Eimac or
>> Amperex. The visible labeling on the  tube  reads:
>> JAN-CIM-5D22
>> Made In USA
>> There is a stamp inside the tube also  that reads:
>> Q8-9034.
>> This tube is tested for emission from a High  Voltage Transformer:
>> 460 VAC through a 15K @ 10 watt resistor to  screen
>> 920 VAC to plate
>> 6.3VAC @ 8 amps to filament
>> -40 VDC to  grid
>> This tube tested at 200 MA.
>>
>> I have no idea about testing and if  that is good to determine tube
>> emission or
>> not.
>>
>> I have one already  and thought I could have a pair for spare tubes for 
>> my
>> 4-400A amp ? I know  .. not exactly the same .. is just plate dissipation
>> the biggest diff?  would Be able to use them as a lower power set of 
>> spare
>> tubes? or just make  another amp with these?
>>
>> I hope replies go to me as well as the list as  the auction will be over
>> in
>> 4
>> hours..
>>
>> Randy -  N2CUA
>>
>>
>>
>>
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