I still have my zerostat. I moved it to the darkroom about 1990, and still clean a record with it now and then.
I modified mine.
I put a rubber insulating sleeve (from the cover of an alligator clip) around the centre crystal chamber, so it does not arc over to the frame as readily.
I also replaced the wire from the crystal frame terminal to the wire spike in the tip with a piece of corona lead wire from an old TV set HV supply, so it would not arc to the frame at it leaves the trigger area.
It now clears dust far and wide, much better than the OEM version. The trick now is to remember to sqeeze and unsqueeze very slowly.
As to the dead ion generator, it sounds like the HV oscillator is not working. It could be anything gone wrong, but would put my money (after a blow fuse) on a dried out electrolytic capacitor or two on some control board inside.