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[AMPS] tetrode as triode

To: <amps@contesting.com>
Subject: [AMPS] tetrode as triode
From: measures@vcnet.com (measures)
Date: Wed, 3 Nov 1999 09:27:42 -0700
>
>i have a 4cx1500b which i want to operate as a triode, mainly to avoid 
>messing with screen and grid supplies. 

A screen supply for the 4cx1500B consists of a string of 5w 20v zeners 
with a high value resistor going to the B+.  This is essentially the same 
circuit that Eimac recommended in its SSB book in the 1950s.  Grid bias 
suppllies are a piece of cake since they supply 0mA.  I would much rather 
do such than mess with 9 g-g tuned inputs using a certain Q.  


>What does the grid dissipation become 
>when strapping screen and control grids together? 

The control grid typically takes 75% of the total grid current, and the 
screen takes 25%.  .  On a 4-400A, which has 10w grid dissipation, this 
is no problem.  Your tube has 1w of allowable grid dissipation.  

> How does one determine the 
>bias voltage in the absence of data? 

Obtain cathode bias from a string of diodes.  Tap string for stated ZSAC. 
 

> Whats are the pros and cons of doing this?

4cx1500B goes kaput due to too much grid dissipation.  
>
ciao, Pino


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


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