The mazzer mini doesn't grind

http://www.fixya.com/support/t27236866-super_jolly_mazzer_grinder_grinder https://www.espressoengineers.com/application/modules/pdfs/assets/upload/Super_Jolly_Mini_-_Instruction_manual1.pdf

your doser mech is possibly gunked up with old grinds, first off try stripping it and cleaning it out, if that doesnt work you may need a new return spring but i think its far more likely to just need a good clean. this is from the mazzer mini but the doser design is pretty much the same so it should help you with disassembly
http://www.home-barista.com/grinders/mazzer-mini-component-photos-t3577.html

1 check the supply wire to swich change if it is not ok 2 chek the swich change if it is not ok 3 if it is automatic check microswiches(one where ground coffee comes out and other below doser) clean from coffee upper swich and try. it block sometime from ground coffee 4 check the windings of electromotor give grinder for if it is not ok 5 check condensator change if it is not ok 6 try to spin the burrs by hand, check if they are not blocked. change bearings if it is not ok
if you need to change bearings you need advice how to open the motor.

Once you have an on/off switch you will remove the bottom panel ans timer, you will see 4 wires, 2 brown and 2 blue. Just make sure you connect brown to brown and blue to blue on the correct terminals. Use your Ohmsmeter to correctly match terminals.

Try this, unplug grinder, vac out all beans, then turn grinder towards fine until you cannot turn the big nut in the center of the burr chamber with your fingers. Now turn adjuster towards coarse until you can barely move the middle nut(you should hear and feel the burs touching) now if you look around the edges of the adjustment ring you will see notches, pick a spot any spot just remember where you started, then turn 14 notches towards coarse, your grind should be almost perfect.

There are 3 springs in the holes around the top neck of the machine, the top part which sits under the collar adjustment knob.

Check the grind setting it might need to be set coarser.

Can the silver collar turn? If yes then adjust, clean out all the grounds then grind for 3 secs, clean grounds then 10 secs(that will give you about 12-16 grams for a test shot). The 3 secs grind and clean is for the coffee that is already ground with the previous setting, there is still a small amount between the burrs and the chute.

Adjust the burrs coarser about 2 numbers.

Easiest way to set the grind on the super jolly is to remove the beans, turn towards fine until you can barely move the middle stem in the grind chamber, then turn towards course about 12-14 notches on the grinding adjuster(not numbers but notches between numbers). If you still cannot get a fine grind and it is not a brand new grinder replace burrs.