AT/ATX power wiring color codes On common PC power supply motherboard connectors, the conductor at pin 1 is typically associated with which wire color(s)?

Introduction / Context:
Technicians working with legacy AT and modern ATX supplies must recognize pin numbering and wire color conventions to avoid miswiring and diagnosis errors. Pin 1 identification varies between standards but is consistently tied to specific color codes.

Given Data / Assumptions:

• Question references “PC power supplies” broadly, implying both historical AT (P8/P9) and ATX main-board connectors may be encountered.
• Color codes follow typical industry conventions (orange for +3.3 V on ATX; white historically used for −5 V on older harnesses).
• We focus on the wire typically present at the Pin 1 position on the main motherboard connector according to common pinout charts.

Concept / Approach:

On the 20-pin/24-pin ATX connector, Pin 1 is +3.3 V and uses the orange conductor. On certain legacy AT harnesses, pin 1 of a given block could use white for a negative rail. Because the stem asks “usually” and presents a pair, the safe, standards-aligned choice that includes the modern norm is “white or orange,” acknowledging both conventions across eras, with orange being the prevalent ATX case.

Step-by-Step Solution:

Verification / Alternative check:

Consult motherboard manuals and ATX specification pinouts, which consistently show orange at Pin 1. Legacy references for AT P8/P9 illustrate white conductors on pin 1 positions in older designs.

Why Other Options Are Wrong:

“Blue or red” and “red or black” do not match the established Pin 1 on ATX. “Red or white” pairs a common +5 V (red) with an older negative rail color, but red is not the ATX Pin 1. Thus, “white or orange” best fits cross-generation expectations.

Common Pitfalls:

Assuming all connectors share the same orientation; ignoring keyed housings; mixing peripheral (Molex) color assumptions with motherboard connectors.

Final Answer:

white or orange.