Duh... I did it again. I accidentally left the bench coaxial switch looking into the sig gen/attenuator, and keyed about 100w from a Kenwood TS-530 in CW mode into it (instead of switching to the dummy load. ZAP! The attenuator let the magic smoke out. Its repaired now, but check out the damage to the 1st 20dB pad :-) ...
