The old power supplies had a large switch that was on the side of the computer to turn on the PC. The small, recessed switch on the back, if it exists, is to select the proper power line voltage. It should only be set to your proper voltage, and never changed while the power supply is plugged into the wall.
A symptom of the voltage switch being in the wrong position (at least if you have 110-120 volt power) would be if the PC doesn't boot all the way up. It might lock up right as the operating system starts to load.
What the voltage switch does is select a voltage doubler circuit if you are operating on 110-115 VAC. Otherwise, the rectifier bridge and capacitors inside are in normal configuration.
The hardware unit that contains the CPU, the RAM, a hard disk, and a power supply is called the "motherboard."
it can simply be called a "power supply" or a PSU (power supply unit)
To keep the power supply cool. If there were no fan the power supply would overheat and fail.
The obvious answer would be the Power Supply Unit (PSU). This starts the computer and without it nothing can work. On the other hand if you have a faulty mother board or RAM, the computer would switch on but nothing would be shown on the screen. The PSU is found on the highest part of the tower. Also check the the switch (if it has) is switched on, and that the power supply cable (the 3 pin one) works.
A computer's (PC's) power supply is a sealed unit and should be replaced as a whole - It is dangerous to try and repair the inside of that sealed unit (that is why it is sealed).
The PSU, Power Supply Unit
A PSU in a system unit is the power supply unit. It provides well-regulated power for the computer and its peripherals.
Yes
The answer is the power supply unit or PSU.
System unit
Top right hand corner of the unit
is an embedded circuit or stand alone unit the function of which is to supply a stable voltage to a circuit or device that must be operated within certain power supply limits .