Wild M20 fine focus stopped working

[skydive1200]

While tracking copepod larva I noticed the fine focus quit working without any indication something broke, like a grinding or clicking. Would any of you folks have experience to share on what to look for or is all hope lost?

[viktor j nilsson]

On the M20, the course and fine focus are completely separate mechanisms. The coarse focus lifts the limb, while the fine focus lifts the stage. When you turn the fine focus knob, you rotate a lever (blue) that is attached to a vertical block (blue) that slides on roller bearings (red). The lever consists of two parts attached with a piece of steel wire. If that wire were to break, I imagine that the fine focus would just stop working as you describe. Maybe that's what happened?



I've taken these apart and it's not too hard. If you PM your email address I can send you schematics that will help.

These focus mechanism almost never break, they are very well built. But I did notice that that wire holding the lever together looked like the most likely piece to fail.

[skydive1200]

With Viktor's guidance, I've got the fine focus working. There was no damage to the microscope found.
I'm assuming during the process of disassembly, whatever configuration made the fine focus fail was lost
so a final determination of cause will not be made. However the linkage design gives me reason to believe it is a prime suspect.
In any event, many thanks go to Viktor and this forum for the support provided.