It's not a question of new or old A7750, but of the extra gears (as said by cornerstone) : on a 7750 the second hand is on the 9 (i think ..). So to move it on 6, the A7750 has been modified with extra gear ......
So the only advice i could give you is to avoid this rep .... and believe me i am as sad as you cause is one of my fav. (mine, going more and more wrong, it's a question of time ..)