[Elecraft] Instability in KPA100 - more

[g3pjt]

Hi

Further to my earlier post I had to disassemble the K2 in order to retighten
the PA devece screws. I removed the extra shield I had put in to kill the
oscillation I reported earlier and low and behold without the screen it
oscilaated again. However when I re assembled the PA with the screen back in
place it still oscillated !
Bearing in mind that the choke RFC10 was suspected as being involved with
the feedback causing this problem I have now removed RFC10. I have looked at
the circuit diagram and I don't understand RFC10 function ( is this a left
over from the days when we used high voltage PAs and this choke was a safety
feature against failure of the anode blocking capacitor ?  :<)).
Anyway it doesn't oscillate anymore.
However I am wondering if I have a component failure coming up ( visual
inspection looks OK)

I will probably dissassemble the KPA and inspect the bottom of the board as
well next time I have the lid off.

73 and thanks for the help,

Bob G3PJT