Jim -
Generally not a good idea.
This pops up every once in a while. The concept is that the PA stage is
a LINEAR amplifier, and the BIAS current is set for the most linear
operation.
Just as an extreme example, you COULD crank the bias up way past cut-off
(zero bias current), and run the PA as Class C if you had enough drive.
But then you're into the clicks, harmonics and even spurs that come
along with Class C.
The Drake PA is operated in Class AB1, for the cleanest amplification
possible. Best to run it that way. Idle current is only drawn 'between
dots' and briefly waiting for the VOX to drop out. Not significant.
Run the tubes as designed, and they will last many years. Spend five
minutes tuning up into the 'wrong' or 'no' antenna and reach for your
wallet!!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-B, C-Line&
TR-4/C Service Supplement CDs
<www.k4oah.com>
[email protected] wrote:
Greetings to the group,
After all the posts lately about the care and feeding of the 6JB6
finals I have what may be a dumb question .....but here she goes.
I have a T4XC that I use exclusively on CW. I think I recall some
while back that someone said the idle current could be reduced
from the standard .07 A level if the transmitter was only being used
on CW. Is that true and if so what level would be appropriate ?
My T4XC looks to have original Sylvania finals and they seem healthy
as I get about 140w out on 20m if I run it full out.
I never run it over 100w and have a fan sucking air up from the cage.
But if I could perhaps get longer life from the tubes by
running less idle current then I might ought to try it. Is this a
good idea or maybe not ? thanks for any thoughts Jim N5KY
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