Hi,
The decks may run slow on 50 Hz as they were intended for 60 Hz.
That depends on how the motors are driven.
***
If the motors rely on the supply frequency for their RPM, they will run slow,
but they may have stepped diameters to accomodate this by moving
something on the shaft.
***
The motors may not rely on the supply frequency for their RPM, they may
have some different speed regulation altogether,
in which case you should not have a problem with that.
***
The difference in construction of 60 Hz transformers and 50 Hz transformers
is very slight. I have never known it have any noticeable effect on small
supply transformers like the ones you refer to.
John