[Amps] toroid filament choke?

[Will Matney]

There's one way to tell how hot it will get. Use any six volt or other 
voltage source which is the same as the heater voltage, apply a 
resistor, the same as the heater, in series with a coil of wire of the 
size like 20 gage and apply current for about one second or a little 
less. Then, check to see how hot the wire gets. 16 gage is rated for 10 
amperes in conduit, and 3.687 amperes at 750 cir mils per ampere. 500 
cir mils per ampere is close to 1/2 the conduit rating. So 16 gage would 
be 5 amperes, and for 3 amperes you would need 18-1/2 gage. 20 gage at 
750 is about 1.463 amperes and at 500 is about 1.7 amperes. 20 AWG 
conduit rating is 3.3 amperes. Just a rough estimate, say at 2 ohms, and 
6 volts, the current would be 3 amperes. At a cold state, I'd say it's 
like 1/2 ohm maximum. 1/2 ohm would be 12 amperes. The resistance could 
be less than this and most likely is. A check with a good low ohm VOM 
would tell that.

Will Matney


k7fm wrote:

>Will said:
>
>"It takes up to one minute + for the heater to reach operating temperature.
>A cold heater is only a few ohms, and that's a lot of current."
>
>Although it will take up to 3 minutes for the cathode to come up to
>operating temperature, the heavy current draw only lasts a moment.  Do not
>confuse the two events.  Heavy current draw is for less than a second, and I
>believe normal current draw is within 2 seconds.
>
>Colin  K7FM
>
>
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