Rosewill Computer Case 422 Informacje Techniczne Pobierz pdf (Strona 53)

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Chapter 4 • Disassembly and Power

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one end of a wire to the other, it should show no resistance. If the wire has a break in it,

the meter shows infinite resistance. Figure 4.18 shows examples of a good wire reading

and a broken wire reading.

Always unplug a computer before working inside it

The power supply provides power to the motherboard, even if the computer is powered off.

Leaving the power cord attached can cause damage when replacing components such as

the processor or RAM.

Good connection Broken wire

Figure 4.18 Sample resistance meter readings

Digital meters have different ways of displaying infinity. Always refer to the meter manual

for this reading. When checking continuity, the meter is placed on the ohms setting, as shown

in Figure 4.18. The ohms setting is usually illustrated by an omega symbol (Ω).

Polarity is not important when performing a con-

tinuity check. Either meter lead (red or black) can be

placed at either end of the wire. However, you do need

a pin-out diagram (wiring list) for the cable before you

can check continuity because pin 1 at one end could

connect to a different pin number at the other end. An

exercise at the end of the chapter steps through this

process.

The same concept of continuity applies to fuses.

A fuse has a tiny wire inside it that extends from end

to end. The fuse is designed so that the wire melts (breaks) if too much current flows through

it. The fuse keeps excessive current from damaging electronic circuits or starting a fire. A fuse

is rated for a particular amount of current. For example, a 5-amp fuse protects a circuit if the

amount of current exceeds 5 amps.

Dealing with small connections and a

meter

Some connectors have small pin connections. Use

a thin meter probe or insert a thin wire, such as a

paper clip, into the hole and touch the meter to the

wire to take your reading.

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Rosewill Computer Case 422 Informacje Techniczne Strona 53