Voltage fluctuating too much. How to fix?

Using Arduino General Electronics
13

I received this 9V adapter, 650 mA. It outputs 9.21V without load.

The voltage is better (5.07V on 5V pin) but when I turn the LCD backlight on it still drops to 4.67V.

Is there a way at all to keep a constant 5V on the 5V pin?