6.4. Power Connectors

A computer uses many different types of power connectors. They include the main power, floppy, peripheral, 12 volt (+12V2DC), and serial ATA (SATA) connectors.

6.4.1. The ATX main power connector

On new power supplies, the ATX main power connector is a 24-pin Molex 39-01-2240 connector. In many cases, it is a 20+4-pin connector for backward compatibility with older version 1.3 motherboards. This is a keyed connector, so you cannot connect it the wrong way without a lot of effort. You can see this and other connectors in Figure 6-1.

Table 6-2 provides you with the pin configuration and voltage supply for the 24-pin Molex main power connector. When troubleshooting faulty power supplies, you need to know what power is supposed to be supplied by each pin in the power connector so that you can identify that the issue you are troubleshooting is related to a problem of power supply.


The main power supply connector provides power at 3.3VDC, 5VDC, and 12VDC.

6.4.2. The floppy drive connector

Although floppy drives are nearly obsolete, the floppy connector is an AMP 171822-4 four-pin connector; see its pin configuration in Table 6-3. This connector provides power to a floppy drive at 5V but can supply power at either 5V or 12V to support devices from manufacturers that decide to use this connector.

Figure 6.1. Power connectors that may be used on power supplies.
Table 6.2. Pin Configuration for the Main Power Connector
2+3.3VDC ...

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