[Elecraft] K3 loss of power (KPA3 100W)

[Lee]

If I had to guess, I would say the finals are blown in my KPA3.

If I advance the power knob, output is normal up to 12 watts.  As soon as
the power is advanced to 13 watts, the power drops to near 0, perhaps 1/4
watt.

Any help on troubleshooting?

Assuming the finals are blown, is it possible to just return the KPA3 to
Elecraft for repair, rather than the K3 itself?

Thanks for any help!  Lee