[Amps] 4-1000 Bias

[Dave White]

>From memory I think I used about 10 volts.  I the W6SAI Radio Handbook there's a circuit to apply a dynamic bias that works by rectifying drive power and using the voltage swing to switch a darlington transistor (I think I used a pair of 2N3055s or something) to apply bias from a zener diode on at standby or between dits/words and off when transmitting.  It works quite well.  If I can find the circuit of my 4-1000A amp and that book I'm happy to scan the relevant bits and mail them over if it helps

Cheers
Dave G0OIL  

----- Original Message -----
From: Wayne Rogers <n1wr at chesapeake.net>
Sent: 01 March 2011 17:38
To: amps at contesting.com
Subject: [Amps] 4-1000 Bias

I have a 4-1000 g-g homebrew amp.  It was designed 4000 volts on the plate. 
My new supply is 5500 volts under load.

With the grid at ground potential and at 4000 volts on the plate the no 
signal grid current is 40 mA. and the plate current is 170 mA, which seems 
right.

At 5500 volts on the plate and the grid at ground potential Ig is 80 mA. and 
Ip is 300 mA. which seems a bit high. My plan is to add bias to the grid. 
How do I determine what the correct operating point is for grounded grid? 
At 300 mA. I'm dissipating .3 X 5500 = 1650 watts which is way over the 
tubes rating.

Thanks,  Wayne N1WR 

_______________________________________________
Amps mailing list
Amps at contesting.com
http://lists.contesting.com/mailman/listinfo/amps