Does anything happen when you try to turn it on? Do you get any sound trying to play the radio?
As a last resort, couldn't find a 7040 manual, but this comes from the 7060:
Resetting the Microcomputer
The microcomputer may malfunction (unit cannot be operated, or shows an erroneous display) if the power cord is unplugged while the power is ON, or due to some other external factor. If this happens, execute the following procedure to reset the microcomputer and return the unit to its normal operating condition.
Unplug the power cord from the wall outlet, then plug it back in while holding down the POWER ON/STANDBY key.
• Please note that resetting the microcomputer will clear the contents of the memory