Anyone have a 12AX7 they hate?

[Why not Pluto?]

My hartke 7000 has now burned up 2 preamp tubes. The first tube lasted like 20 years and the second one lasted maybe 20 seconds! I figured I may have a problem. After changing some noisy and swollen capacitors It might be fixed. Anyone have any tubes that sound real bad? I would hate to sacrifice a nice tube that could live a full life of gigging.