[Amps] 4-250A testing

[Carl]

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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