What are these O rings?
I have a spare attenuator if the installed one is blown. Not sure if it's compatible or not but it's an electronically-switchable type and does 10 through 70dB. Model number's 8495K. I was in the process of building a switching unit for it so it could be used as a stand-alone job for any of my other pieces of test equipment. If the faulty one in the 8566B is irreparable then I guess I'll just have to forget the stand-alone project and swap it out for the duff one. <shrug>
Jinxie