hp 20b - Performing Complete Self Test
Press ON PMT + all 3 button at the same time.
Display ‘Tst Screen’
Perform the screen test by pressing any key 12 times.
It should return to Display ‘Tst Screen’.
Press the DOWN arrow then INPUT.
Display ‘Tst Keyboard’
Perform the keyboard test.
Press ON PMT + at the same time (3 button simultaneously). Press [ON/CE] key to exit test.