Compaq 12XL510 Models XL300, XL300A, and XL300B - Maintenance & Service Gu - Page 74

Presario 1200XL Series Model XL300, XL300A, and XL300B Removal Sequence This chapter provides details for removing and replacing each component of the Presario 1200XL units. Electrostatic Discharge When removing or replacing parts, be careful to discharge static electricity before touching the internal Notebook components. A sudden discharge of static electricity from a finger or other conductor can destroy static-sensitive devices and microcircuitry. Often the spark is neither felt nor heard, but damage occurs. An electronic device exposed to an electrostatic discharge may not seem to be affected and continue to work perfectly throughout a normal cycle. However, the discharge degrades internal layers, which reduces the operating life of the device. Networks built into many integrated circuits provide some protection; but in many cases, the discharge contains enough power to alter device parameters or melt silicon junctions. The table below shows the amount of static electricity generated by common activities associated with servicing computers. Electrostatic Voltage Event Relative Humidity 10% 40% 50% Walking across carpet 35,000 V 15,000 V 7,500 V Walking across vinyl floor 12,000 V 5,000 V 3,000 V Motion of bench worker 6,000 V 800 V 400 V Removing DIPS from plastic tubes Removing DIPS from vinyl trays Removing DIPS from styrofoam Removing bubble pack from PCBs 2,000 V 11,500 V 14,500 V 26,000 V 700 V 4,000 V 5,000 V 20,000 V 400 V 2,000 V 3,500 V 7,000 V Packing PCBs in foam-lined box 21,000 V 11,000 V 5,000 V Ä CAUTION: As little as 700 Volts can degrade Notebook components. Be sure to ground yourself before touching the Notebook or its subassemblies. PRESARIO NOTEBOOK MAINTENANCE AND SERVICE GUIDE 1200XL SERIES REMOVAL SEQUENCE 1