Frequency of AC for electronic devices
Frequency matters if any of the following are true:


If there is a synchronous or induction motor in the device. These run at or close to mains frequency so they will run 20% faster on 60 Hz than on 50 Hz. This includes motor driven mains clocks.
If there is a transformer in the device it may be only rated for 60 Hz. 50 Hz transformers are slightly heavier and have different laminations.



  A 60 Hz rated transformer can only be used on a 60 Hz system (with certain exceptions -- read further.) Whereas a 50 or 50/60 Hz rated transformer can be used on either a 50 or a 60 Hz rated system.
  Exception: If the energizing voltage does not exceed 83% of the transformers nominal voltage, the transformer can be used. Remember that transformers are simple ratio devices and the output will also be lower. Another important factor to remember is that the transformer`s capacity will also have to be derated at the same ratio of the applied voltage divided by the nominal voltage. Source: Schneider Electric.


Devices affected include microwave ovens and devices with larger transformers such as hi-fi systems, etc.


If an electronic device uses the mains frequency for timing such as a digital clock or an old TV.
If the device uses in-line inductors such as the ballasts on AC fluorescent tubes (as opposed to high-frequency driven) the impedance will vary. \$ Z = 2 \pi f L \$ where Z is the impedance and L is the inductance.
If the device uses a rectified DC supply the smoothing capacitors have to be larger for 50 Hz supplies as the capacitor "top-up" pulses are less frequent.





Universal motors don't care.
Devices with variable frequency drives convert the mains to DC before chopping it back to AC. These don't care.
Most electronic devices are DC internally so provided the PSU is 50 / 60 Hz capable there is no problem with them.