Problem metalica 2004-01-20 21:39:38: Roughing pump valve broken

[bleen at snf.stanford.edu]

The roughing pump will no longer open as the valve appears disconnected from the knob.  While i was opening the valve to pump down, and while almost fully open but with the knob still not providing any resistance to turning, i heard a pop like a spring breaking and the LN2 stopped bubbling.  After this the knob will not screw in all the way and when fully out there is no pumping.  Sounds like the knob broke free from the valve controlling the opening and closing of the pump.