[Elecraft] KPA-1500 failed!

[lists at w2irt.net]

I was operating in the ARRL-CW contest this morning and on 20m, with a 1.2:1
SWR on the Yagi, all of a sudden I saw my power drop to about 450-500W with
about 40W in. Worked a few stations but not as easily as when I turned
everything on this morning. Switched over to phone and made a few contacts.
Audio is fine barefoot with 100W out of the K3s-which suffered blown finals
itself during CQWW SSB last fall, but with the amp in I got reports that my
audio was badly distorted. 

Before I send it in, is there anything I should look at or any diagnostics I
can easily perform? For the cost of this, I'd have thought protection would
have kicked in to prevent anything untoward from happening. I'm in complete
disbelief, to be honest.

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73 and Good DX
Peter, W2IRT