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[Amps] Passive grid:

To: <amps@contesting.com>
Subject: [Amps] Passive grid:
From: 2@vc.net (Rich)
Date: Fri, 29 Nov 2002 16:26:43 -0800
>
>
>Rich wrote:
>
>> >
>> >
>> >Rich wrote:
>> >
>> >>
>> >>   At least 800 screen V are needed.  The simplist and safest
>> >> screen supply is a zener-string shunt regulator at the lv end of the hv
>> >> bleeder.
>> >
>> >Hi Rich,
>> >
>> >I have always worried about using a zener string from the HV supply for the
>> >screen. What happens if the plate choke or something else should open in 
the
>> >plate circuit?
>>
>> The high-ohm resistor limits I.
>>
>> >Also if one were to turn off the HV supply and key the rig before the HV
>> >decayed to zero, you could have low plate voltage but still have full 
screen
>> >voltage. That would mean very high screen current.
>> >
>> not with a resistor to limit I.
>> >73
>> >Gary  K4FMX
>> >
>
>Hi Rich,
>
>So you would need to use a resistor of a high enough value that would 
>limit zener
>current to around maximum screen current that would be expected?

Yes

>Then is it ok to run maximum screen current and maximum screen voltage with no
>plate voltage?

When the anode/plate V disappears, there is no current through the 
resistor that delivers current to the screen regulator, so the screen has 
0V/0A.

cheers, Gary 

-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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