Study Lab for Chapter 5

Use the "Key Terms and Definitions" section of the lab to review terms used in this chapter. Try the "Practice Test" to check your comprehension of the chapter. Tackle the "Lab Exercises" to apply your knowledge.

Key Terms and Definitions

115 120V/60 cycle

AC standard used in North America.

230 240V/50 cycle

AC standard used in Europe, Japan, and other world areas.

AC (alternating current)

Power supplies convert AC into DC.

air dam

A barrier to freely flowing air inside the case; usually caused by ribbon cables.

analog multimeter

Multimeter with a needle and scale readout.

ATX power supply

A power supply form factor similar in size to Slimline, but with a keyed 20-pin connector. Some ATX power supplies have an on-off switch, but this is not required.

ATX-12V

An addition to the ATX standard to support the Pentium 4 processor. ATX-12Vcompliant power supplies have a 4-pin connector to provide additional +12V power.

auto- ranging

A multimeter that determines the correct voltage level automatically.

auxiliary

A 6-pin power connector required by some motherboards.

blackout

Complete loss of electrical power.

brownout

A voltage dip below acceptable levels.

continuity

Tests fuses or cables to determine if a signal passes through the device properly.

DC (direct current)

The power supply distributes DC current to the motherboard, drives , and other peripherals attached to the computer.

digital multimeter

Multimeter with a digital readout.

EMI/RFI (electromagnetic interference/radio-frequency interference)

Some high-quality surge suppressors minimize EMI/RFI to provide more reliable power.

IEEE-587A

IEEE standard for surge suppressors.

line-interactive

Another name for a true UPS.

multimeter

An electrical testing device that can be used for DC and AC voltage and polarity, resistance, diodes, continuity, and amperage.

negative pressure

Cooling method used by most power supplies; the power supply fan creates a weak vacuum to draw air through the system.

outlet tester

Device that plugs into a wall outlet to determine if wiring is properly grounded or polarized (doesn't test current levels).

overloading

Connecting devices to a computer that require more watts than the power supply can support.

parallel test

An electrical test (such as for voltage) in which the multimeter is not part of the circuit, but is parallel to it.

Power Good

A signal that is used by the motherboard to determine if the system can continue to run. If Power Good is too high or too low, the system is automatically rebooted.

resistance

Tests resistance (ohms) of a device.

series test

An electrical test (such as for amperage) in which the multimeter is part of the circuit.

SFX

A power supply form factor that is designed for Micro-ATX and Flex-ATX systems. It uses the same connector as the ATX power supply, but comes in two varieties. The more common SFX-S has the AC power connector along the short side of the power supply enclosure, whereas SFX-L has the power connector along the long side of the power supply enclosure.

Slimline power supply

A power supply form factor with a 12-pin connector and a power switch on a cable. Used by Baby-AT and LPX motherboards. Also called LPX or PS/2 power supply.

spike

Momentary overvoltage.

SPS (standby power supply)

A battery backup unit that switches to battery power only when AC power fails. Most so-called UPS units are really SPS units.

surge

Sustained overvoltage.

surge suppressor

Device that blocks harmful power surges (overvoltages) from reaching your computer.

true UPS

Provides power from the battery to the system at all times; it has no switchover time.

UL-1449

UL standard for surge suppressors.

UPS (uninterruptible power supply)

Provides battery power to connected equipment if a power outage occurs. A true UPS provides continuous battery power at all times, compared to a standby power supply.

VA (volt-amp)

The most common measurement used for battery backup units. Multiply watts by 1.4 to determine VA.

wattage

A measure of heat; power supplies are rated in watts.

Practice Test

1:	The computer reboots itself after it's been turned on for a few minutes. Which of the following procedures is the best way to determine if the power supply is failing? (Choose one) Test the +3.3V DC line. Test the Power Good line as soon as the system is turned on. Test the Power Good line after the system reboots itself. Replace the power supply with a higher wattage rating immediately.
2:	The power supply is rated for 300 watts. The upgrades you plan to perform use about 230 watts. The minimum wattage rating of the power supply you should install should be equal to or greater than which of the following? (Choose one) 235W 400W 350W 300W
3:	The power supply fan is not spinning. Which of the following repair steps should you should you try first ? (Choose one) Check for short circuits inside system. Check input voltage switch. Use multimeter to check Power Good. Check power connector to motherboard.
4:	Which of the following changes to a system can disrupt internal airflow? (Choose all correct answers) Remove add-on card. Install new ATA cable and ATA or ATAPI drive. Add slot covers to all empty slots. Install new Serial ATA drive.
5:	You need to test the power supply on a Baby-AT computer with a Slimline power supply. Which of the following connectors contains pin 1 (Power Good)? (Choose one) P9 ATX-12V P8 Auxiliary
6:	Your computer has an SFX power supply. Which of the following should you determine before ordering a replacement? (Choose one) Whether the power connector is 12-pin or 20-pin Whether the power supply has an on-off switch The location of the power supply's AC cord connector Whether the power supply handles 115V or 230V AC
7:	You need to test the Power Good line on the power supply with a multimeter. Which of the following settings is correct? (Choose one) Amperage DC voltage Ohms AC voltage
8:	A multiple-outlet device has a UL-1363 rating, whereas another one has an IEEE-587A rating. Which of the following is correct about these devices? (Choose one) Both are surge suppressors. Neither is a surge suppressor. The UL-rated device only is a surge suppressor. The IEEE-rated device only is a surge suppressor.
9:	You need to order a battery backup unit for a computer with a total wattage of 420. For longer battery life, you should select a battery backup unit with a VA rating at least twice the VA requirement of the unit you want to protect. Which of the following VA ratings is closest to twice the VA requirement for this computer? 900 1,200 1,000 1,400
10:	As soon as you connect a hard disk drive to the system, the computer can't start. It was necessary to share a power connector between a case fan and the drive. Which of the following are the most likely causes for this problem? (Choose two) The hard drive is overloading the power supply. The Y-splitter might have a dead short. The hard drive has not been formatted. The hard drive has not been partitioned.

Lab Exercises

Required equipment : working system, multimeter, Internet connection, parallel printer cable, ESD protection (wrist strap, antistatic mat), tools to open system

1. Determine wattage rating for current power supply.

2. Check manufacturer or third-party suppliers" Web sites: Is a bigger (more watts) power supply available?

3. Use multimeter to check power supply voltage and Power Good.

4. Use multimeter to check parallel cable continuity (see pinouts in Chapter 8, "Input/Output Devices and Cables").

Answers to Practice Test

A1:	Answer C (testing the Power Good line after the system reboots itself) is correct. If you test the Power Good line as soon as you first start the system, the problems that cause the system to reboot ( overheating or overloading) haven't occurred yet.
A2:	Answer C (350W) is correct. Using the 70% of marked rating as a rule of thumb, a 350W power supply reaches 70% of its rating at 245W. Note that a 400W power supply (answer D) is a better choice, but this question asked for the minimum. The others don't offer enough safety margin.
A3:	Answer B (check input voltage switch) is correct. You can check the input voltage setting without opening the system.
A4:	Answers A (remove add-on card) and B (install new ATA cable and ATA or ATAPI drive) are correct. These changes can disrupt airflow if the slot cover is closed or if the wide ATA cable is not secured out of the way. The other options improve airflow.
A5:	Answer C (P8) is correct. P9 is the other Slimline power connector, whereas the other two choices are used with ATX power supplies.
A6:	Answer C is correct. SFX power supplies come in two variations (SFX-S and SFX-L), depending upon the location of the AC cord connector. The other answers don't apply to this type of power supply.
A7:	Answer B (DC voltage) is correct. Power Good is located on the power supply connector to the motherboard, which uses DC voltage.
A8:	Answer D (IEEE-587A only) is correct. The correct UL rating for surge suppressors is UL-1449.
A9:	Answer B (1,200VA) is correct. The VA (420 wattsx1.4) for this unit is 588, and 2x588 is 1,176. The other values are too low (900 and 1,000) or significantly more than twice the VA requirement (1,400).
A10:	Answer B (the Y-splitter might have a dead short) is correct. If the Y-splitter checks out OK, the drive itself might have a short. An overloaded power supply would start, but might overheat or reboot itself, and the hard disk's format or partition status is not relevant here.