Module 12- Section 3-narrated

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Information about Module 12- Section 3-narrated

Published on March 2, 2014

Author: pmgreenwald1


Module 12- Section 3: Module 12- Section 3 Finishing Electricity 1 IV. AC vs DC Electricity: IV. AC vs DC Electricity A. AC (alternating current) Associated with voltage at the wall receptacle USA – line voltage averages 115 volts at 60Hz at the receptacle but is rated at 120V 60 Hz Europe – Line voltage is 220 Volts at 50Hz at the receptacle 2 A. AC (cont): A. AC (cont) Wall receptacle arrangement: The longest opening in the receptacle is neutral the shortest opening is the hot the “circular” is the ground 3 Hot, Neutral, and Ground (continued) Figure 1-31: Hot, Neutral, and Ground ( continued ) Figure 1-31 4 Hot, Neutral, and Ground: 5 Hot, Neutral, and Ground AC travels from power station to house on a hot line AC travels from panel to device using black (hot) wire AC flows out of device circuit in a white (neutral) wire AC returns to power station on a neutral line PowerPoint Presentation:  Normally, electricity flows from hot to neutral to make a closed circuit in the controlled environment of an electrical device such as a lamp 6 Transformers step down voltage from the power station to the home (Fig 1-30): Transformers step down voltage from the power station to the home (Fig 1-30) 7 A transformer keeps power constant but changes the ratio of current to voltage Courtesy: Course Technology/Cengage Learning Hot, Neutral, and Ground (continued) (Fig. 1-32): Hot, Neutral, and Ground ( continued ) (Fig. 1-32) 8 Measuring Line Voltage: Measuring Line Voltage Line voltage between hot and neutral should be about 115 - 120 Volts 1.   S et the multi-meter to “Volts AC ” 2.   Set voltage range to the highest range 3.   Insert the probes: one into neutral and one to the hot then adjust the voltage range 9 Foreign Travel: Foreign Travel To check to see if a computer device is configured for the 220-240 V 50 Hz AC power delivered in European countries look at its electrical specification faceplate. Also note that the wall outlets are shaped differently- so you will need converter plugs. 10 PowerPoint Presentation: Single-voltage device: INPUT AC120Vac 60Hz 200W Dual-voltage device: INPUT AC120/240V 50-60Hz 1300W Multi-voltage device: INPUT AC100 — 240V 50-60Hz 14W OUTPUT DC 1.2V 2.3A 11 PowerPoint Presentation: 12 PowerPoint Presentation: Also- check charging packs (the brick) 13 A converter plug set: A converter plug set 14 B. DC Electricity: B. DC Electricity DC: Direct Current Electronic circuitry operates on DC current The computer’s power supply converts AC to DC . 15 PowerPoint Presentation: Inside the power supply, a Transformer steps down line voltage Rectifier converts the stepped down line voltage and current to DC A rectifier is made up of 4 diodes A diode allows current to flow only one way in a circuit (DC). 16 PowerPoint Presentation: Capacitors smooth out the signal that the rectifier produces so that it fluctuates by a small, but acceptable, amount. Capacitors inside a power supply can hold a dangerous amount of charge. 17 PowerPoint Presentation:  Capacitors on a motherboard or other circuit board often have embedded crossed lines on top 18 C. DC Output of PC Power Supply: C. DC Output of PC Power Supply +12 volts – yellow wire +5 volts – red wire ground – black wire These are standard- other colors are not standard. 19 C. DC Voltages (cont): C. DC Voltages (cont) Orange wire: ATX mainboard- +3.3 V On an ATX, Power Good is a gray wire NOTE: The term “rail” is used to describe each voltage line in a PSU. 20 C. DC Voltages (cont): C. DC Voltages (cont) All drives get +12v and +5v and ground wires +12v drives the motor +5v is used by the circuitry These voltages are supplied through the 5-pin Molex connector. 21 Computer Power Supply (2-45): Computer Power Supply (2-45) 22 PowerPoint Presentation: Some Power Connector Types: IDE drives: Molex Floppy Drives: mini (formerly Berg) SATA- 5-pin SATA power connector P1: 24-pin mainboard connector P4: 4-pin 12 V auxiliary connector for older mainboard using the 20-pin connector 23 PowerPoint Presentation: 6-pin and 8-pin PCIe connectors may also be provided (the 8-pin usually has two detachable pins for backward compatibility). 24 Connectors on a PC power supply: Connectors on a PC power supply 25 D. Measuring DC Voltage: D. Measuring DC Voltage Set the multi-meter to DC Voltage Set the voltage to its highest range Place the black lead into a ground Place the red lead at the point to measure (typically in a power connector) Adjust the voltage range 26 PowerPoint Presentation: 27 Power Supply Tester: Power Supply Tester 28 E. Power Supply Types and Connectors: E. Power Supply Types and Connectors AT Supplies (obsolete): Have two power connectors (P8 and P9) Rule: 4 black wires meet in the middle ATX Supplies (prior to 2003): Use 1 20-pin connector Uses “soft power”, need to unplug PC to completely remove power 29 PowerPoint Presentation: All ATX supplies provide “soft power” even when the PC is off. To work inside an ATX PC, use the secondary PS switch on the supply to remove all power from the mainboard (or unplug it). 30 PowerPoint Presentation: 31 ATX12V v1.3: ATX12V v1.3 ATX supplies used with the Pentium 4 processor use an addition, 4-pin square connector that connects to the mainboard near the CPU This is called an “auxiliary” connector and is designated as P4. 32 PowerPoint Presentation: 33 ATX 12V v2.3 or 2.31 standard : ATX 12V v2.3 or 2.31 standard New power supplies follow the ATX 12V standard (which is the same as ATX v2.0 and above). The main difference with ATX: One 24-pin mainboard connector Increased efficiency Support for PCIe Dual 12V rails 34 PowerPoint Presentation: 35 PowerPoint Presentation: The ATX12V v2.3 is the most recent power supply standard (released in 2007). The ATX 12V v2.31 revision is newer- however, it is not sufficiently different to worry about. 36 Other Power Supply Standards: Other Power Supply Standards The EPS12V v2.1-v2.92 stands for “entry-level Power Supply” and is a standard used for servers. Despite its unfortunate name, it is a high-reliability power supply, however, the ATX12V typically provides more power. 37 PowerPoint Presentation: Mini-ATX and Micro-ATX: small form factor PSU TFX12V: for low-profile systems SFX12V: for use with flex-ATX mainboards 38 Two Other Terms:: Two Other Terms: Efficiency: the ATX12V standard requires a power supply to be at minimum 70% efficient Active PFC: PFC stands for power factor correction – these eliminate “harmonics” on the electrical power grid 39 Measuring Continuity: Measuring Continuity A. What to Measure Continuity of: Cables Connectors Fuses The resistance of these items is ideally zero. 40 Two Extremes of Resistance:: Two Extremes of Resistance: 1. Zero resistance - (0 ohms, 0  ) Zero resistance is desirable in cables, connectors, and fuses Good cables, circuit traces, and fuses have “ continuity ” which is 0 ohms and which indicates a good connection. 41 Second Extreme of Resistance:: Second Extreme of Resistance: 2. Open circuit - infinite resistance Open circuit - no current can flow across an open circuit Desirable for an open switch Undesirable in electrical components or in wires, cables, or fuses 42 PowerPoint Presentation: Continuity is required to connect electrical items together. If the connectors have too much resistance, current flow is restricted and the light bulb (or whatever) will not work properly. 43 PowerPoint Presentation: When measuring the resistance of cables and wires, a reading of 0.00 (or just 0) indicates a good connection. If the connection is broken, the meter reads “off scale” on all resistance scales. This can be expressed several different ways. 44 PowerPoint Presentation: Resistance is NEVER measured in a live circuit (power on) Ideally (to avoid the influence of nearby resistances) isolate the device to be measured. 45 B. How to Measure: B. How to Measure Set the multi-meter to Resistance Adjust meter to the highest range Attach the leads to the device being measured Reduce resistance range Ideally the resistance is zero, if it is not, the cable, fuse or connector is bad 46 C. Continuity Setting: C. Continuity Setting Some multi-meters have a “continuity” setting, symbolized by a speaker If the component being tested has zero resistance, a buzzer will sound 47 PowerPoint Presentation: Typically, only resistance and voltage are measured by a PC technician. Resistance of cables, wires, connectors and other devices is measured outside of the PC and with power off. The voltage provided by the power supply is measured inside the PC with the power on. 48 PowerPoint Presentation: Resistance and voltage are measured using a multi-meter set to the proper function. Multi-meters can also measure current and other electrical quantities but these are not measured for the PC. 49 V. Troubleshooting Power Problems: V. Troubleshooting Power Problems The power supply can cause trouble and show up in any component RAM trouble Hard drive Spontaneous Rebooting Operating system troubles It’s difficult to track down the problems 50 A. Fan Not Operating: A. Fan Not Operating See if the fan is clogged (dust and fur get into it) Whining, humming sounds Bearings are bad, fan will fail. Another component could be shorted Drawing too much current, which causes draining of power to other components 51 B. Other Problems: B. Other Problems Spontaneous Rebooting or Failures: Power supply under-rated Drive going bad Power supply going bad Power supplies contain CAPACITORS!- dangerous to fix (typically replace). Do not wear ESD device! 52 Protect Yourself Against Electrical Shock and Burns: 53 Protect Yourself Against Electrical Shock and Burns Four Ways to Protect from electrical shock a. Disconnect power Disconnect plug at AC outlet b. Protect power cord Do not pull on cord itself Identify trip hazards c. Remove jewelry PowerPoint Presentation: d. Power supplies and CRT monitors contain capacitors Technician must not be grounded Both considered field replaceable unit (FRU) 54 PowerPoint Presentation: This is the end of the third seciton of Module 12. 55

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