[Amps] Purpose of cathode resistor?

[R.Measures]

On Dec 28, 2005, at 10:15 AM, Steve Thompson wrote:

>
>
> TexasRF at aol.com wrote:
>>
>> If the fuse blows, the cathode voltage can rise to near the plate  
>> potential.

> That was my immediate thought, but won't the cathode stop rising once 
> it
> reaches the tube's cut off bias?

During an intermittent VHF parasite, the tube is driven briefly into 
full conduction -- resulting in an anode-cathode potential of perhaps a 
couple of hundred volts drop.  With an anode supply of several kV, when 
the large accompanying current surge blows the cathode fuse, the 
potential across where the fuse was spikes to over a couple of thousand 
volts before the tube gets biased to cutoff.
>
> Steve
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>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org



Richard L. Measures, AG6K, 805.386.3734.  www.somis.org