[Amps] warm up time for TX tubes

[Jim Thomson]

Date: Sun, 10 Apr 2016 14:15:10 -0400
From: "John Flood" <k4dlx at bellsouth.net>
To: <amps at contesting.com>
Subject: [Amps] warm up time for TX tubes
New to this reflector.  
Hope someone can help me understand tube warm up requirements.
Specifically, What are the necessary conditions for voltages at plate ,
screen and control grid during Warm up for indirectly heated tetrode tubes.
I have seen directions that say no plate voltage during warm up, but some
amps (MLA2500) apply plate voltage and limit cathode current to a few mA by
self-bias during warm up.


What I have in mind for my amp with gu74b  (4cx800) is to apply fil voltage
for 3 minutes while screen is at 0v, plate is full on and 
G1 is biased to cutoff (approx. -75v).  

Is my approach workable?
And What are the necessary conditions condition for the tub during warm up?..
Thanks in advance for your help

John  K4dlx  

##  there is no requirement to shut off the B+   while the fil is heating up.
All that is required is to have the plate current biased to cut off.... just like
RX, and  no drive applied.

##  with full B+,  nothing will happen..as long as no drive applied, and plate
current cut off.   Even Eimac sez the same thing.

Jim   VE7RF