This video goes through the painful disassembly of a late 1980's era HP 48SX scientific calculator and the replacement of the rubber compression stripped used to aid in making the contact between the keyboard assembly and the main mother board. The symptoms for this failure can be that the calculator will not power on or there is intermittent or no operation on some keys. A quick check is to press bezel above the white function keys while pressing the on button. If the calculator turns on or the keys resume function, then the internal compression strip has deteriorated beyond reliable use and must be replaced. Please watch the video to learn how to replace that compression strip if the symptoms are the same.