Newwer CN-90F Follow Focus Fix
Not too long ago I reviewed a very affordable follow focus unit ($37), the Newwer CN-90F. It wasn't bad, but had too much play or "slop" in the knob that rotated the focus gear. It was wobbly and took too long to reverse direction. Comments on that video reported that others had used the product without the play I had experienced. After taking the unit apart and investigating, it turns out there is an easy fix for this problem.
First you must remove the rod clamp hardware found on the bottom rail of the unit. This is super easy, as all you have to do is remove the adjustment nut and screw and the rod hardware falls right off. Next, remove the three Philips head screws that attach the aluminum adjustment rail to the gearbox (see above).
Once the adjustment rail is gone, you'll have access to four more Philips head screws that are recessed inside the plastic gearbox (see above). Tighten all four of these and you're done! The play in the knob is now significantly reduced and you should have more precise control when pulling focus with this unit.
While this fix has no effect on the overall quality of the unit (it's still made of cheap plastic), it does affect performance. The feel is so much better now that it increases the value and makes the $37 spent that much more of a deal. If your unit was like mine, I highly encourage this fix. All you need is some precision screwdrivers and about five minutes and you're on your way.