[Elecraft] Unusual 10 meter-PA tripped out

[Bob Allen]

I hope this hasn't already been figured out, sorry if it has. Rig is S/N 
3162
I was CQing with the K3's digital voice recorder on 10 meters yesterday 
at 100w, I noticed that the SWR is bouncing up to the 3+ end of the 
scale on the voice peaks. I stopped, checked the SWR with the K3's 
bridge, SWR=1.6:1 and the MFJ-969 tuner also read approx. 1.5:1, so I 
kept CQing and after 5-10 minutes the circuit breaker for the PA tripped 
and wouldn't reset until it cooled down.
Then I turned down the output to about 70w and CQed for about 20 minutes 
more with no more trouble.
I took the K3 to a friend's QTH and the SWR bouncing to the 3+ range was 
the same but I didn't run it long enough to see if the circuit breaker 
would trip.
Any thoughts?

Bob
KB1FRW
73