Why when I connect the cable from PSU to CPU my PC doesn’t start?

Troubleshooting Power Connection Issues: Why Your PC Doesn’t Boots When Connecting the CPU Cable

Building or maintaining a computer can sometimes present perplexing challenges, especially when unexpected behaviors occur during assembly or troubleshooting. One common issue is when a PC fails to start after connecting the power supply unit (PSU) cables, specifically the CPU power connector. Understanding the root causes and appropriate solutions can help you resolve these problems efficiently.

Understanding the Role of the PSU Cable Connections

A typical desktop PC requires several cables from the PSU to supply power to various components. Key among these are the main 24-pin motherboard connector and the CPU power cable, usually an 8-pin (or 4+4 pin) connector. Proper connection of these cables is critical for the system to power on correctly.

Common Symptoms and Observations

When all PSU cables, including the CPU connector, are connected, the PC does not start. The fans and lights may flicker briefly, then stop.
Disconnecting just the CPU power cable enables the PC to power on, but Windows does not detect the monitor signal.
Reconnecting the CPU cable results in no boot, and the system remains unresponsive.

Possible Causes and Troubleshooting Steps

Incorrect or Faulty CPU Power Cable
Cause: The CPU power cable might be damaged, incompatible, or not seated properly.
Solution: Inspect the cable for visible damage. Ensure it’s the correct cable for your PSU and motherboard. Re-seat the connector firmly, ensuring it clicks into place.
Improper Connection or Seating
Cause: Loose or improper connection can cause short circuits or prevent the motherboard from powering on properly.
Solution: Turn off the PSU and disconnect it from power. Carefully disconnect and reconnect the CPU power cable, ensuring it aligns properly with the motherboard socket. Confirm there are no bent pins.
Power Supply Unit (PSU) Issues
Cause: An underperforming or faulty PSU may cause symptoms like flickering fans or prevent system startup.
Solution: Test the PSU with a known working unit or use a PSU tester. Alternatively, try connecting the system with a different PSU to isolate the issue.
Motherboard or CPU Short Circuit
Cause: Short circuits caused by incorrect installation or damaged components can halt startup.
Solution: Check for any loose screws, standoffs, or debris