CompTIA®A+ Exam Notes : Install A Power Supply Based On Given Specifications

1. PC Hardware

1.9 Install a power supply based on given specifications.

Power Supplies :

1. DC voltages commonly found in a PC:

  • +5, and +12 volts are the DC voltages commonly found on PCs. 80386 / 486 operate at +5v
  • Pentium and above operate at +3.3v
  • Power supply wires - yellow=+12v, blue=-12v, red=+5v, and white=-5v

2. One good way of determining a bad power supply is that the fan will not rotate. Also, the computer will not boot and the LED s indicating the power and disk activity will be OFF.

3. ATX12V 2.0 power supply provides four different voltages

  • 3.3Volts, 5Volts, 12Volts and -12Volts. Previous versions of ATX12V used to provide
  • -5V, and it has been discontinued in version 2.x.

4. ATX style systems use two power connectors, P8 and P9 to connect to the motherboard. ATX systems use only one P1 connector to connect to the motherboard.

5. Uninterrupted Power Supply (UPS)

An UPS is required for any critical and un-interrupted use of computers. It has the following benefits:

  • Provide protection against small surges
  • Filters noise from entering the computer
  • Provide power to the computer during line power failure
  • Give stable power to computer, even when the line power is unstable

Note that the UPS can give un-interrupted power only for a fixed amount of time under a given load, in the absence of line voltage.

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