hp 12c (platinum) - Performing Keyboard Self Test
This is a simple test to check that all the keys are working properly on your 12c or 12c Platinum.
To perform the keyboard / display test, with the calculator off, press and hold the divide key, press and release the ON / OFF key, then release the divide key.
Press each key in order from left to right on each row, from the top row to the bottom row. As you press the keyboard, for the first (top) row 4 segments will be displayed at any one time - so this gives you a chance to check the display (or dead pixel). And on the second to fourth rows, you see only 2 segments. You need to press through the Enter key twice, once when testing the 3 row, and second time when testing the 4 row.
At the end of the test, it should show 12 or 0.00.
If your key sequence is wrong, you will get ‘Error 9’. Press Enter and repeat the test.