[Amps] Problem with 500w AM Linear with mosfet IRFP360

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Sun, 11 Apr 2010 09:18:45 -0700 (PDT), sasas asasas
<tzitzikas_ee at yahoo.com> wrote:

>Without driving power, we must adjust the current at 200mA (when the linear is cold).
>My problem is this: When i tried to adjust the current at 200mA without driving power, when the current close to 
>160mA (by tuning the variable resistance 5Kohm) suddenly the current takes the value 3A and some smoke comes out
>from the input transformer. 

REPLY:

It sounds like it is breaking into oscillation. I notice there is a
transformer, T3, which is there to provide negative feedback from
output to input. Perhaps the phase has gotten accidentally reversed?
That would make it oscillate. 

73, Bill W6WRT