First, unplug the power supply from the inside of the casing and connect the green and black P1 connectors with the telegraph cable. Power on the power supply. Then the power supply will turn on the fan.
The first step is to assume that the power supply is good. Of course, the power supply is good, of course. The power supply converts AC to DC, so you only have to look at DC when measured in meters. Therefore, the metering channel must be rotated towards the DC Volt. Yes. Once the DC Volt is turned on, the channel of the meter must be turned to the appropriate voltage. The power in the computer is limited to a maximum of 12V. So you measure wires that are less than 10 volts by 10 volts. 12 volts is measured by 50 volts.
You also need to know how the power supply wires in your computer work. The strings are colored. The colors are different and the voltages are different. There are seven colors. Yellow is +12 volts. Red is 5 volts. Orange is 3.3 volts. Brown is 3.3V sense; Blue is -12 volts; White is -5 volts. Purple is +5 volts. Green is power on; Gray is power good; Black is the ground. That is why it is said that only 12V is used in most computers. Move the metering channel to the nearest 10V.