between the ring nut and the shaft. Tighten the ring nut, using your spanner tool if
necessary, until the shaft turns freely, but does not wobble or feel loose. Then, tighten the
small set screws in the ring nut to hold it in place.
When adjusting the ring nut, bear in mind that the assembly will loosen up a bit after a
period of use. If it is too loose now, it will only become looser later. There is a very fine line
between too loose and too tight. You will find yourself making very small changes in the
tightness of the ring nut to achieve the best compromise.
Worm Shaft End Play
If either of the worm shafts is able to slide back and forth in its bracket (end play), you'll
have excessive slop in the mount. To adjust the end play of either worm, start by removing
the large silver nut on one end of the worm bracket. This reveals a threaded insert (or
sleeve) through which the worm shaft passes. This insert can be turned to adjust the
amount of end play in the worm. Too loose, and the axis will be very sloppy. Too tight, and
the axis will be stiff. It may take several tries to find the happy medium.
On both of my CG-5s, there were several very small, very thin plastic washers in the worm
assemblies. These washers are nearly invisible when buried in the thick factory grease, so
it's easy to miss them. Look carefully!
Another description of this adjustment comes from fellow CG-5 owner
Jim McKay. Note
that the worm assemblies on Jim's CG-5 contained no plastic washers! This is indicative
of the variation you can expect between different examples of the CG-5.
I went ahead and removed the nut [on one end of the worm housing]. The
nut holds a threaded sleeve in place. One end of the sleeve bears directly
on the worm while the other end of the worm bears directly on the worm
housing. There are no plastic washers on either end of the worm as there
are inside the mount. The threaded sleeve can be threaded in and out of
the housing thereby increasing and decreasing the amount of endplay in
the worm. You then lock it in place with the hex nut. It would appear that
you need a small amount of play otherwise the worm becomes very difficult
to turn. I was able to take most of the play out and retighten the nut again.
The nut is 16mm and is on fairly tight (I used a 1/4" drive metric socket
set). I first took the worm housing off the mount and put it in a vise (with
something to cushion the metal jaws of the vise), but I later found out that it
can be loosened while the housing is still attached to the mount. Adjusting
the sleeve made a BIG difference in the slop that I was experiencing in the
RA axis. The DEC axis was fine and I didn't touch it. My guess is that
without any washers between the worm and the housing, wear at the ends
of the worm will necessitate adjustment at a later date.
Although I did not have any endplay in the worms of the first CG-5 I refurbished, my
second CG-5 required this adjustment. Unlike Jim's mount, mine had plastic washers in
both worm assemblies. I was able to remove the endplay almost entirely while maintaining
very free movement of the worm.
Worm Gear Mesh
This is the most tedious, but arguably the most important adjustment of all. Here, we are
adjusting how deeply the worm meshes with the teeth of the large silver worm gear.
The small set screw between the two larger silver hex head screws on the worm assembly
controls how deeply the worm meshes with the teeth of the worm gear inside the mount. If
the gears mesh too tightly, the worm shaft will be stiff and difficult to turn. If the two gears
do not mesh enough, the axis will have backlash and "slop."
Turning the set screw clockwise pushes the worm farther from the worm gear, loosening
the axis. Turning the set screw counter-clockwise lets the gears mesh more deeply,
tightening the axis and reducing backlash. Proper adjustment consists of making small
