[NLRS] FET amp question

[W0ZQ at aol.com]

Glen, its doesn't sound good.   Here  are some simple things to check .... 
you may have tried these  already.

1).   Is the device in right ?   The  mounting tabs are Source.   There are 
two side tabs.   The  side tab with the cut in it is the Drain, or output.   
The side tab  without any cut in it is the Gate, or input.    Make sure that it  
is oriented correctly AND that the body (Source) is indeed in electrical 
contact  with ground and not floating for some reason.

2)   The output  (Drain) should have pretty much Vcc on it.  If your PS is 28 
vdc, then it  should be close to 28 vdc too.

3)  The input (Gate) should be  several volts, perhaps 3 to 5 vdc.

4)  Take a hard look for any  shorts that should not be there.   Look over 
the PCB closely to make  sure that its what its suppose to be ..... no opens or 
shorts, no flaws,  especially in the input and output circuits.

5)  Those darn RF feed  through caps.   You may want to try replacing both of 
them (input and  output) just to rule out a broken feedthru cap.   This one 
has bitten  me before.

6)   Your DC power supply is robust enough under  load right .... its not 
sagging when you go to apply RF drive  ?

7)   You have good faith that you are indeed delivering RF  drive to the 
board .... not a bad coax or bad connector.

That all I can  think of.   If the voltages are OK, the parts in right, no 
obvious  shorts or opens, you have replaced the feedthru caps, your getting RF 
drive to  the board, about the only thing left is the device.

73, Jon
W0ZQ  




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