So ill say it again please unplug the system before

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So I'll say it again. Please unplug the system before you attach these grounding cables. Old power supplies had a physical switch that broke the current between the wall and the power supply when shut off. New supplies don't do that. Even when the system is turned off, it still supplies a continuous current to the motherboard so if you have this case here with the power supply and it was plugged in with the system off, you might think you're safe, but you're not because there is still a current going through the system. Granted, on the motherboard side of the power supply, it is DC current and it probably won't hurt you that much, but if the power supply were to have a fault and was leaking AC current to the system,you would still be in trouble. So as a general rule of thumb, unplug the system before you start usinga static mat. Summary 3:44-4:03 That's it for this lesson. Remember that when you're working on a PC system, you need to prevent electrostatic discharge damage. The best way to do that is to invest in a good static mat and to use it properly. Also remember to unplug the system while you're working on it. You don't want to be hooked up to that 110 volts through a static mat.
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Static electricity is the accumulation of an electric charge (produced by friction) on a non-grounded object. The static charge on the surface of a non-grounded object can jump when it contacts the surface of any grounded object. This electric discharge is known as electrostatic discharge (ESD). ESD can be very destructive to a computer. The threat of ESD begins when the fragile components (including the processor, hard drives, memory, motherboard, and expansion cards) inside the computer are exposed. Damage can occur simply by placing a fingertip too close to a component inside an open computer case. ESD charges can travel through wires and into components, where the wires can explode or fuse together, causing the components to fail. ESD can cause immediate failure of components, or could gradually degrade components, causing only intermittent problems. It takes very little ESD to damage a component. A discharge of as little as 300 volts can damage a component, but 3,000 volts or more of ESD must occur before you can even feel it. Implement the following measures to protect against ESD. Keep the relative humidity in the room high, ideally around 70%, and temperature between 72-77 degrees. The key is to avoid dry air in the computer repair location to prevent ESD. Use antistatic mats under the PC and on the floor. Discharge yourself before touching any computer component. When touching anything inside the computer, wear an antistatic wrist strap that is attached with an alligator clip to the metal PC chassis. Ground both yourself and the computer to the same ground. This provides a single path for the flow of electrical potential.
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