FW: [AMPS] Shunt regulated high voltage psu

[rich]

>
>
>
>> Rich said:
>> 
>> >//  Why not use a simple zener-string  shunt regulator and obviate the 
>> >needless complexity?
>> 
>> Because they don't regulate well enough. John, GW4FRX, did a lot of work on
>> this some years back, and showed that zener regulation of the screen 
produced
>> far more splatter than electronic regulation.
>> 
//  The quality of regulation depends on using quality zeners and 
understanding the Looneytunes dissipation ratings  --  i.e., don't exceed 
more than c. 35% of the diss. rating and put the zeners in the path of 
airflow to the 4cx250 sockets.  
  
>> It may well be good for HF, but not for VHF.
>> 
//  I built a 2x 4cx250R 2m linear-amplifier that delivered 900w PEP.  
When loaded for c. 5mA of screen-current it was as clean as the Kenwood 
TS-700 10w SSB transceiver that drove it.  The screen was operated from a 
400V zener string that was biased from a 100k‡ resistor connected to the 
+1200V tap in the +2400v FWD anode supply.  Screen V-regulation was quite 
good.  Current in the 100k R was c. 8mA.  Thus c. 10w was consumed by the 
screen supply zeners and 100k dropping R.  

cheers, Peter

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
end


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