My leak detector suffered another defect. I was just doing some tests of the filling manifold while the filament was suddenly turned off and the needle of the vacuum gauge went out of the scale. After some time spent by looking for the problem, I found that the transformer is really hot, 110°C, that was really bad. It meant that there would be probably shorted winding.
I finally got a new custom transformer from Bohemia Trafo, good communication, great quality and reasonable price of around $60, the transformer has 9 windings!
I still havent finished the repair yet, but it looks it will be OK..