[ARC5] 3A5 Filament Voltage Question

[J. Forster]

Hi Les,

I've got the data sheets, thanks.  I like the idea of running it at 1.2
VDC with a couple of diodes as OVP.

Best,

-John

==============


>   John,
>   I looked at 3 data-sheets for the 3V4 type "tube".
>   The last sheet referred to  type 3V4WA, by Tung Sol.
>   It described the 3V4WA as "a ruggedized version of the 3V4, making it
>   suitable for military operations".
>   I know you understand the significance of "W" suffix in the valve type
>   designation.
>   The datasheet gave a method to test the ability of the "tube" to
>   withstand vibration.
>
>   The datasheet says this about the filament:  "Absolute maximum rating
>   of the filament voltage (Ef) shall be 1.25 +/- 20% VDC.
>   Interestingly it does not give a rating for the series connected
>   filament.  Only mentions 1.25 volts in THREE places.
>   So (you can do the maths!) 1.25/5 equ 0.25 volts, giving a working
>   voltage of 1.0 to 1.5 volts.
>
>   If you want to see the datasheets I have, pls let me know.
>   On the other hand, if you don't want to see them, don't tell me, and I
>   won't send them.
>
>
>   73 de Les Smith
>   vk2bcu at operamail.com
>
>
> On Sun, Aug 4, 2013, at 10:18, J. Forster wrote:
>> I'm playing with an ART-4 Transmitter. This unit is for reporting the
>> blast intensity near an airplaned towed target tube (sock), hence the
>> closeness of the shell to target can be estimated.
>>
>> Anyway, after tracing the circuit, it has an oscillator and an amplifier
>> stage.
>>
>> The filament on the 3A5 is parallel wired.
>>
>> The spec sheet says 1.4 VDC, Max. A current alkaline battery will put
>> out
>> significantly more than that.
>>
>> I want to run the thing off an adjustable DC supply, and allow some
>> margin.
>>
>> Does anyone know roughly what the minimum DC filament voltage to apply
>> for
>> enough emission to work reasonably well? I just want to test the
>> operating
>> frequency and get a rough idea of the modulation deviation.
>>
>> Thanks,
>>
>> -John
>>
>> ===================
>>
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