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Hi Arthur and Eric,

    I've drawn up a simple schematics to illustrate the parts of the entire bubble unit. The key parts were two bellows hidden under the Knob. Bellow ② is usually filled with fluid and bellow ① with air.

      When turning the knob clockwise, movement of the threaded rod attached to bellow ① would stretch bellow ② and compress bellow ① itself at the same time, therefore causing certain amount of liquid in the bubble chamber to be drawn back into bellow ②, and a small portion of air from bellow ① is forced into the bubble chamber, compensating the negative pressure caused by less fluid in the chamber. The effect is reversed if the knob is turned in the opposite direction.

   Eric, you may try the method which Arthur has demostrated in his superb article as a start, by my knowledge if sufficient fluid still remain in the bellow, and a half volume of fluid is successfully injected into the chamber through the filling port, chances are that the bubble unit will be restored to working order if you fiddle with the unit a few times(tilt and turn,tilt and turn...)  If the result is not very promising, then one ought to suspect that a leak or leaks may have occured. 

    Simple way to check if there is a leak:1.fill the bubble chamber with as much fluid as you possibly can. 2.seal the filling port properly. 3.unscrew the knob assembly and rotate the unit into a bellow straight-down position and  squeeze the bellow. If a leak is present on the bellow, you should start to see a tiny stream of fluid shooting out from the leak.  If no fluid can be observed shooting or seeping from the bellow surface no matter how hard you squeeze the bellow, then fortunately the bellows are still intact.  

      If the unit has completely dried up and you still cant get sufficient fluid into the chamber through the filling port, then you may follow my method: remove the entire lamp fixture first. Once it's been removed, turn the unit upside-down, you should se a threaded ring securing a piece of think round glass in place, uncrew the ring and remove the glass, by doing so you will have the entire bubble chamber exposed, you can get the job done by simply pouring fluid into the chamber and reseal it(make sure the bellow sucks in some fluid). 

      Arthur,since leaks in the bellow is exceedingly small(See second pic),I used a fine cordless soldering iron to patch up these holes with tin,after that a tiny drop of epoxy super glue would be applied to the soldered holes for reassurance.

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