[Amps] LF oscillation caused by defective plate choke?

[Vic K2VCO]

   I am using a 25 ohm 50w wirewound glitch resistor immediately after the
   plate choke. I have 0.01 uf 6 kV discs in parallel with 0.001's on both
   sides of the resistor and at the HV connector. I presume that the resistor
   functions as a choke.

   On 10/9/2013 4:37 AM, Jim Thomson wrote:

     ###  points well taken.   The typ 50 uh choke will resonate at aprx 35
     mhz...so no worry about series resonances in ham bands.
     That’s actually a good design.   I have no clue how much rf Voltage..is
     too much ?    But with tubes with handles etc, we are dealing with way
     more  than  2000  V...so  the  simple  extra LC would be of a great
     benefit...and easy to implement.
     Jim  VE7RF
     -----Original Message----- From: peter chadwick
     Sent: Wednesday, October 09, 2013 4:03 AM
     To: Jim Thomson ; [1]amps at contesting.com
     Subject: RE: [Amps] LF oscillation caused by defective plate choke?

     ###   250 uh is fine for the plate choke.     Instead of the 1000 pf
     bypass cap,  use 2-3 x 4700 pf disc ceramics.     That combo makes for an
     excellent lower freq bypass cap.

     Then wire 1-3 x  500pf ceramic doorknob caps in parallel with the 4700 pf
     caps.   The 500 pf caps make for an excellent higher freq bypass cap.<
     You will have about 1 volt across that combination on 80m. Using 1 4700 pF
     cap and 1 500 pF cap in parallel will give 3 volts: then a 50 microhenry
     choke and another 4700 pf will drop this to 27mV and you have saved 1 or 2
     500  pF caps and 1 4700 pF cap and got a better result. Just adding
     capacitors gets to a state of diminishing returns.
     73
     Peter G3RZP
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--
Vic, K2VCO
Fresno CA
[4]http://www.qsl.net/k2vco/

References

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