Good job Nino, looks like a new one

To test the mechanism itself to make sure it is advancing and not getting stuck I have used a 12V gell type battery and I think I have used a 9V battery too. Simply use a jumper cable to connect 1 side of battery to the coil. Do the same with the other side too but only momentarily touch against battery and it will pull in and advance the unit. The polarity is not important, but step it through a whole cycle to see if it gets stuck.
I found if it gets stuck you may need to get a new spring or increase tension on spring by putting a new loop on the spring and maybe adjust the little wiper arms at the side.

Sometimes the nylon ratchet or the shiny plate will be worn too in which case it may require replacement. These are not expensive and Pinball Resource have them too. Part numbers for these are:

GTB-A9014 AS Relay Armature ( The shiny Plate) $4.20 Each
GTB-D8755 As Relay Spindle ( Whit nylon ratchet/cog wheel )  $2.90 Each

Sorry to hijack your thread Nino, I have had to do this on my Card Whiz before so I thought it important to include the above info.

Chris