A keypad is a set of buttons arranged in a block or "pad" which bear digits, symbols or alphabetical letters. Pads mostly containing numbers are called a numeric keypad. Numeric keypads are found on alphanumeric keyboards and on other devices which require mainly numeric input such as calculators, push-button telephones, vending machines, ATMs, Point of Sale devices, combination locks, and digital door locks. Many devices follow the E.161 standard for their arrangement.
1. see if all backlights on keypad is complete
(remember that missing backlights on 3110c unit can cause no lcd light too)
2. if all backlight is in tact....use tester to check the lines..
3. if you see this line is broken... just APPLY jumper as shown on the image below...