Dell Vostro 3581 Service Manual

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Contents

Dell Vostro 3581 Service Manual Manual pdf 7 page image

NOTE: To avoid electrostatic discharge, ground yourself by using a wrist grounding strap or by periodically touching anunpainted metal surface at the same time as touching a connector on the back of the computer.Electrostatic discharge—ESD protectionESD is a major concern when you handle electronic components, especially sensitive components such as expansion cards, processors,memory DIMMs, and system boards. Very slight charges can damage circuits in ways that may not be obvious, such as intermittentproblems or a shortened product life span. As the industry pushes for lower power requirements and increased density, ESD protection is anincreasing concern.Due to the increased density of semiconductors used in recent Dell products, the sensitivity to static damage is now higher than in previousDell products. For this reason, some previously approved methods of handling parts are no longer applicable.Two recognized types of ESD damage are catastrophic and intermittent failures.• Catastrophic – Catastrophic failures represent approximately 20 percent of ESD-related failures. The damage causes an immediate andcomplete loss of device functionality. An example of catastrophic failure is a memory DIMM that has received a static shock andimmediately generates a "No POST/No Video" symptom with a beep code emitted for missing or nonfunctional memory.• Intermittent – Intermittent failures represent approximately 80 percent of ESD-related failures. The high rate of intermittent failuresmeans that most of the time when damage occurs, it is not immediately recognizable. The DIMM receives a static shock, but thetracing is merely weakened and does not immediately produce outward symptoms related to the damage. The weakened trace maytake weeks or months to melt, and in the meantime may cause degradation of memory integrity, intermittent memory errors, etc.The more difficult type of damage to recognize and troubleshoot is the intermittent (also called latent or "walking wounded") failure.Perform the following steps to prevent ESD damage:• Use a wired ESD wrist strap that is properly grounded. The use of wireless anti-static straps is no longer allowed; they do not provideadequate protection. Touching the chassis before handling parts does not ensure adequate ESD protection on parts with increasedsensitivity to ESD damage.• Handle all static-sensitive components in a static-safe area. If possible, use anti-static floor pads and workbench pads.• When unpacking a static-sensitive component from its shipping carton, do not remove the component from the anti-static packingmaterial until you are ready to install the component. Before unwrapping the anti-static packaging, ensure that you discharge staticelectricity from your body.• Before transporting a static-sensitive component, place it in an anti-static container or packaging.ESD field service kitThe unmonitored Field Service kit is the most commonly used service kit. Each Field Service kit includes three main components: anti-staticmat, wrist strap, and bonding wire.Components of an ESD field service kitThe components of an ESD field service kit are:• Anti-Static Mat – The anti-static mat is dissipative and parts can be placed on it during service procedures. When using an anti-staticmat, your wrist strap should be snug and the bonding wire should be connected to the mat and to any bare metal on the system beingworked on. Once deployed properly, service parts can be removed from the ESD bag and placed directly on the mat. ESD-sensitiveitems are safe in your hand, on the ESD mat, in the system, or inside a bag.• Wrist Strap and Bonding Wire – The wrist strap and bonding wire can be either directly connected between your wrist and bare metalon the hardware if the ESD mat is not required, or connected to the anti-static mat to protect hardware that is temporarily placed onthe mat. The physical connection of the wrist strap and bonding wire between your skin, the ESD mat, and the hardware is known asbonding. Use only Field Service kits with a wrist strap, mat, and bonding wire. Never use wireless wrist straps. Always be aware that theinternal wires of a wrist strap are prone to damage from normal wear and tear, and must be checked regularly with a wrist strap testerin order to avoid accidental ESD hardware damage. It is recommended to test the wrist strap and bonding wire at least once per week.• ESD Wrist Strap Tester – The wires inside of an ESD strap are prone to damage over time. When using an unmonitored kit, it is a bestpractice to regularly test the strap prior to each service call, and at a minimum, test once per week. A wrist strap tester is the bestmethod for doing this test. If you do not have your own wrist strap tester, check with your regional office to find out if they have one.To perform the test, plug the wrist-strap's bonding-wire into the tester while it is strapped to your wrist and push the button to test. Agreen LED is lit if the test is successful; a red LED is lit and an alarm sounds if the test fails.Working on your computer 7