[Amps] 833 plate cathode capacitance

[Jim Thomson]

Date: Tue, 5 Oct 2010 01:44:58 -0400
From: "Fuqua, Bill L" <wlfuqu00 at uky.edu>
Subject: [Amps] 833 plate cathode capacitance


Finally got around to it and measured the plate to cathode capacitance.
I was quite surprised. It was as high as stated in specs. I got about 20pF but that includes
a few pF from setup wiring.
   I thought I'd try another tube that has similar dissipation and characteristics 304TL.
Its plate to cathode capacitance was less than a pF. 
So even grounded grid operation with a 833A may not be stable with out some neutralization. 

Used spectrum analyzer and tracking generator.  Measured feed thru signal level and calculated capacitance based on 
frequency and input Z of spectrum analyzer. The grid was grounded and signal fed to plate and cathode connected to
spectrum analyzer.



73
Bill wa4lav

##  why not just use a digital LCR meter ?    Factor in the test leads if required, depending on 
spacing between em. 

Jim  VE7RF