[Moon-net] 70cm 4cx250b amp question.

Kim Liljekrans [OZ5IQ] kim at oz5iq.dk
Fri Nov 7 11:35:44 CET 2008


HI VE6ZT , Jordan

Re.:  Ur Amp -  These 4CX250 tubes do have a tendency to  use and generate 
neg.  g2 Current  !! So its NOT wise to use a MOV, - why you only "protect" 
the outer circuit  !

The main protection you should use, is a  1 - 2 W  resistor  ie 47 Kohm, 
connected to gnd from the G2 pin  on the outer socket.

In this manner there is a path to GND, for current  the tube is "generating" 
when making this neg.  G2 current.

Think of the old  Voltage Reg tubes -  when they are running in an Amp,  the 
may " blink" both due to the alternating current comsumption -
THUS were able to consume  the extra current / neg current, these 
4CX150/250 tubes can generate during the alternating level of current flow
in them.  Thats  ITS almost vital to have a resistor to GND as I wrote to 
you.


GL  with the Amp


VY 73  de  OZ5IQ, Kim 


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