Open the door and press the test button on the front of the mpu 4 times. The message center will alternately display "coin" and "coup", press the spin button when "coin" appears in the display. This will make the hopper attempt to dispense 10 coins while the door is open. Observe what the coins are doing in relation to the wheel shelf, the knife, the optics and the runway. That should give you a pretty good idea as to what the problem is. To exit the test mode simply close the door. A word of warning - Do not stick your fingers or any other object into the hopper mechanism while performing this test. Once you've determined the problem power off the machine and remove the hopper before making the necessary adjustments.