Potential problems & remedies: Top disk 'O'-rings
Top disk 'O'-rings become unseated from their grooves
In normal use, it is very unlikely that the 'o'-rings will come out of
their grooves. The grooves have a slight lip to retain the 'o'-rings
under all but the most exceptional circumstances. Indeed, it is
difficult to remove the 'o'-rings, except by picking at the cut edge
where it meets the slot in the top disk.
Problems may however occur if the H-clamp is used incorrectly, for
example, by attaching it with the slotted side of the top disk over the
instrument. When the clamp is tightened, the cut ends of the 'o'-rings
may be squeezed so that they protrude into the disk's slot. When the
clamp is then loosened for removal and slipped off the instrument, the
'o'-rings may be dragged out of their grooves. Alternatively, the
ends of the 'o'-rings that had been squeezed out into the slot may not
retract when the pressure is released. They may then become 'snagged',
for example on the boom when it is swung into the slot, causing the
'o'-rings to be lifted out of their grooves.
In the event an 'o'-ring becomes unseated, it can be reseated easily
by simply pressing it back into the groove. 'O'-rings that have become
detached entirely can also be refitted in this way but if they do not
appear to be long enough to stretch all the way round the disk, from
one side of the slot to the other, the best approach is to start
pressing it into the groove at one edge of the slot and stretch it
gently while pressing it into the groove around the disk, gauging how
much stretch will be necessary for it to reach the edge on the other
side of the slot.
