matched quads, one dead, then what?


My search skills have failed me: if you have a comparatively new (~100hrs) on a new matched set of quads (in this case, winged C EL34's), and one of them dies...is the theory that you replace the whole set of tubes? Or do/can you send one of the functioning ones in to be tested, and have the replacement tube matched to it?

This is why I've started with an inexpensive tube amp, and affordable tubes. :-)
soundgasm
Mlsstl is correct assuming you actually needed a matched quad to begin with. If you have to manually bias each tube in your amp, you really don't need a matched set. The biasing process will take care of variations. Matched don't hurt though.
...and this kind of seemingly random, premature tube failure is to be expected once in a while?
Yes
One of the reasons I purchase my output tubes(matched octets) from Upscale Audio, is the fact that they record all the measurements on the boxes. That would make it a piece of cake for Kevin to perfectly match any tube that had prematurely failed. None have, in the 10+ years that I've been dealing with him, though.