Samsung 920NW Service Manual - Page 6

1 Precautions 1 Precautions Follow these safety, servicing and ESD precautions to prevent damage and to protect against potential hazards such as electrical shock. 1-1 Safety Precautions 1-1-1 Warnings 1. For continued safety, do not attempt to modify the circuit board. 2. Disconnect the AC power and DC power jack before servicing. 1-1-2 Servicing the LCD Monitor 1. When servicing the LCD Monitor, Disconnect the AC line cord from the AC outlet. 2. It is essential that service technicians have an accurate voltage meter available at all times. Check the calibration of this meter periodically. 1-1-3 Fire and Shock Hazard Before returning the monitor to the user, perform the following safety checks: 1. Inspect each lead dress to make certain that the leads are not pinched or that hardware is not lodged between the chassis and other metal parts in the monitor. 2. Inspect all protective devices such as nonmetallic control knobs, insulating materials, cabinet backs, adjustment and compartment covers or shields, isolation resistorcapacitor networks, mechanical insulators, etc. 3. Leakage Current Hot Check (Figure 1-1): WARNING : Do not use an isolation transformer during this test. Use a leakage current tester or a metering system that complies with American National Standards Institute (ANSI C101.1, Leakage Current for Appliances), and Underwriters Laboratories (UL Publication UL1410, 59.7). Figure 1-1. Leakage Current Test Circuit 4. With the unit completely reassembled, plug the AC line cord directly into a 120V AC outlet. With the unit's AC switch first in the ON position and then OFF, measure the current between a known earth ground (metal water pipe, conduit, etc.) and all exposed metal parts, including: metal cabinets, screwheads and control shafts. The current measured should not exceed 0.5 milliamp. Reverse the power-plug prongs in the AC outlet and repeat the test. 1-1-4 Product Safety Notices Some electrical and mechanical parts have special safetyrelated characteristics which are often not evident from visual inspection. The protection they give may not be obtained by replacing them with components rated for higher voltage, wattage, etc. Parts that have special safety characteristics are identified by on schematics and parts lists. A substitute replacement that does not have the same safety characteristics as the recommended replacement part might create shock, fire and/or other hazards. Product safety is under review continuously and new instructions are issued whenever appropriate. 1-1