Marco,
I had a long conversation with a few people and here is what we have come up with for the MC-70 Board.
Now depending on the version
DZ4- is the 24V,50ma,5watt zener OR
DZ4A and DZ4B- are 12V,650ma,5watts each in series.
DZ1- is 15V, 0.2a,1watt
DZ2- is a 3.9V, 20ma, 1/2watt
I have replaced them as required and as needed and have made money in the mean time repairing them locally.
Good Luck