Help to clarify the meaning of a power supply's Voltage and Current rating
The power supply must be the voltage the device requires (within +/-5% or so), and the supply must be capable of delivering at least the current that the device requires.

If you supply 12 volts to a device designed to operate on 7.5 volts, that device will probably be damaged.

If the supply is the correct voltage but cannot deliver the current the device requires, the supply may be damaged or its output voltage may drop to a point where the device won't work (or both!)