HP d248 HP Compaq Business Desktop d200 Series Personal Computers Service Refe - Page 34

Identifying the Chassis, Routine Care, and Disassembly Preparation Microtower Type 2 Chassis Variations Chassis Characteristic d220, d228, d230 d240, d248 Power supply mounting method Removable power supply support bracket No support bracket required Power supply installation method Lay chassis on its side for easiest installation Keep chassis in upright position for easiest installation Lower drive cage retaining screws Four screws on front of chassis Three screws on front of plus one on the side chassis plus one on the side Processor cooling method Air baffle Chassis fan Memory Single channel Dual channel Number of memory sockets 2 4 5.2 Electrostatic Discharge Information A sudden discharge of static electricity from your finger or other conductor can destroy static-sensitive devices or microcircuitry. Often the spark is neither felt nor heard, but damage occurs. An electronic device exposed to electrostatic discharge (ESD) may not appear to be affected at all and can work perfectly throughout a normal cycle. The device may function normally for a while, but it has been degraded in the internal layers, reducing its life expectancy. 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. 5.2.1 Generating Static The following table shows that: ■ Different activities generate different amounts of static electricity. ■ Static electricity increases as humidity decreases. Event Walking across carpet Walking across vinyl floor Motions of bench worker Removing bubble pack from PCB Packing PCBs in foam-lined box Relative Humidity 55% 40% 10% 7,500 V 3,000 V 400 V 15,000 V 5,000 V 800 V 35,000 V 12,000 V 6,000 V 7,000 V 5,000 V 20,000 V 11,000 V 26,500 V 21,000 V ✎ 700 volts can degrade a product. 5-2 336493-004 Service Reference Guide, d200