Repair of slipping gear in Nikon SF-210 and SF-200 batch adapters

One of the failure modes in Nikon SF-200/210 is a worn out worm gear. The symptom is a loud grinding noise during the slide feeding process. In the advanced stage the slide feeder stops working altogether. See notes on the disassembly and repair here:

http://www.shtengel.com/gleb/SF210_disassembly_and_repair.htm

Curiously, I have now seen few times a similar symptoms (slides not feeding properly) due to a different reason - slipping gear.

Here is a photo of the batch loader with the side panel taken off:

Here are the details of  drive mechanism below (curtsey of Victor Ho) and Victor's description of the problem:

Turning gear #4 will advance the rubber band allowing the slide to advance and eject. If I spin this gear, the mechanism works. Gear #3 spins when I spin #4. But I do not see any movement of #2 or #1.

The worm gear #1 spins. This will engage #2 and it will spin. But gear #3 does not spin. It appears that #3 is offset above #4. #3 and #4 both appear to be intact and not worn down.

Spinning the worm gear (#1) only will spin gear #2 – slowly. The gears #3, 4 do not spin and the black band does not advance or eject the slide. #3 or #4 have to turn and cause the black band to advance/eject.

This happens because the gear #3 is not seating properly. Upon careful examination one can see that there is a groove on the shaft on which the gear #3 sits, and a pin in the gear #3 that moves along that groove (see below).

So the gear #3 can move. I do not know why it was designed this way - probably safety precaustion, but it can have two positions - "low" and "high". In order for the adapter to works properly, the gear #3 needs to be in a "low" position

You start with a gear #3 in "high" position, see below:

In order to move it into the "low" position, push the gear #3 down by about 1/4" (5-6mm), and then rotate counter-clockwise by about 1/4 turn, see below:

Once you release it, the gear comes up about half-way and stays in "low" position.

The adapter should work properly now:

See other views of the same process below: before (left) and after (right):