When the IC is burnt, this may indicate an defective motor (shortcut...). If so, your IC replacement and work will be lost soon again. Also the motor may be blocked mechanically - can you turn it manually?

I'd strongly suggest to test the motor first, before any other attempts to repair. Does somebody have figures, how much current the motor will draw in normal (DC) operation, at which voltage?

The motor is not blocked mechanically, its movement is very smooth when manually rotated. Voltage drawn by the motor is 7.5-8.0 volts. Current drawn by the motor varies respective to the activities.