[Amps] Screen voltage regulation

[R.Measures]

On May 14, 2004, at 3:01 AM, Angel Vilaseca wrote:

> Hi,
> To ensure screen protection, how about connecting a string of diodes=20=

> between
> plate and screen with its cathode connected to the plate?

=F0  The screen and the anode/plate are at greatly different potentials=20=

during the RF cycle. Putting a string of diodes between the two=20
elements would cause a serious problem when they conducted.  A simpler=20=

way of protecting the screen would be to put a string of zener diodes=20
from the screen to the ground, with the zener bias obtained from the=20
high voltage bleeder resistor.  This would limit screen current to a=20
safe value and also provide a sink for reverse screen current.

cheers.

> If the plate supply fails, then the extra diodes will put the plate at=20=

> the
> same voltage as the screen, so most (not all) of the electrons should
> hopefully continue flowing to the plate.
> I have never actually tried this. I saw it in a german magazine some=20=

> years
> ago.
>
> Any opinions?
>
> Angel Vilaseca HB9SLV
>
> "R.Measures" wrote:
>
>> On May 12, 2004, at 11:34 AM, Thomas Hoeppe wrote:
>>
>>> Hello guys,
>>>
>>> I am new on this reflector, so may be I am asking a question whitch
>>> has been discussed before.
>>> I am looking for a simple design for the regulation of a screen
>>> supply. I need 800V and about 50 mA. I will have to take care of =
some
>>> negative current, so the supply has to be able to do that or I will
>>> use a 100mA supply and allow 50 mA of current through a resistor to
>>> ground. My anode voltage is 5 KV, so I don't want to get the G2
>>> voltage from the anode voltage.
>>
>> For my current tetrode-with-handles A/AB1 project, I am using a
>> semi-simple 1500v resonant-choke filter screen supply with a 50k-ohm
>> 100w bleeder and No electronic V regulator --  such as:
>> http://www.somis.org/D-a-08.GIF
>> -   The logic is that with a resonant-choke filter, the screen
>> regulation will be good enough and that 30mA of shunt-current will
>> handle negative/reverse screen current during tune-up.  Collins used =
a
>> resonant-choke filter screen supply on the 30L-1, so I thought I =
might
>> give it a go.  If it's not good enough, there's a 1600V tap on the
>> transformer to allow for the series pass regulator circuit above.
>>
>> good luck, Tom
>>>
>>> I am looking for easy and rugged solutions. (KISS.......keep it=20
>>> simple
>>> and stupid!)
>>>
>>> Any ideas?
>>>
>>> Thanks in advance.......
>>>
>>> Tom, DJ5RE (DL0AO crew)
>>>
>>>
>>>
>> Richard L. Measures, AG6K, 805.386.3734.  www.somis.org
>>
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>
>
>
>
>
>
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org