[Elecraft] help!

[Merlarts at aol.com]

Yes help,
 
If it ain't one thing, it's another.  Having just fixed the AGC  problem in 
my K2 (2631), enjoying the beautiful radio, weirdness has again  struck.  
 
I get high SWR on 40 meters after I cut the output down, to raise it again  
for full output.  When I back the power off to minimum, there's the high  
reflected power indication, about 9 to one.  When I run the power back up,  the SWR 
again behaves.  Souns like antenna glitches, no?
 
The antenna is a big loop (240 feet) open at the top, fed with 450 ohm open  
wire line.  I use an SGC 230, and the combination with my K2-100 has been  
perfect.  When I back off the power, only on forty meters, the SWR goes  crazy.  
Only on forty.  All other bands tune thru the tuner just  fine.  So, thinking 
still it must be the antenna, I ran the K2 into a dummy  load.  Same Thing 
Happens !!!!!!!!!
 
Is there a bad solder joint in the low pass filter on the K2?; that lets it  
operate at some power levels but shows high levels of spurious transmitted  
signal sometimes?
 
I don't get it.  Any ideas?
 
Merlin, W3ICT,  merlarts at aol.com