PC not getting into bios, with no diagnostic lights

Understanding and Troubleshooting a Non-Responsive PC Without Diagnostic Indicators

Introduction
Encountering a non-booting PC can be frustrating, especially when critical diagnostic signals are absent. In this article, we’ll explore a common scenario where a desktop system refuses to POST (Power-On Self-Test), presents no display, and shows no motherboard diagnostic lights, despite the hardware appearing to be powered on. Using a specific setup as a reference, we’ll analyze potential causes and outline structured troubleshooting steps to identify the root of the problem.

System Specifications
The system in question comprises the following components:
– CPU: AMD Ryzen 5 3600X
– Memory: 2x8GB DDR4 RAM
– Graphics Card: Radeon RX 5700
– Motherboard: ASUS TUF GAMING B550-PLUS
– Power Supply: Adequate wattage PSU

Background
This PC was functioning reliably for four years before suddenly becoming unresponsive. The user reports that the system now exhibits the following symptoms:

Symptoms
– No display output or boot screen
– Absence of diagnostic LEDs on the motherboard (no boot, VGA, CPU, or DRAM lights)
– Chassis fans spinning normally
– Motherboard RGB lighting operational
– The power button does not respond to long presses or other inputs
– CPU temperature remains normal (not overheated)

Initial Observations
The system powers on (fans spin, RGB lights up), yet it fails to POST, and diagnostic LEDs remain silent. This suggests that the motherboard is not reaching any BIOS or hardware initialization stage detectable via onboard indicators. The unresponsive power button indicates potential power or motherboard control issues. Importantly, the CPU does not feel hot, which helps eliminate thermal failures or immediate CPU damage signs.

Troubleshooting Steps Taken
The user has already attempted several standard fixes:
– Clearing the BIOS (e.g., CMOS reset)
– Replacing the PSU and GPU with known-good components
– Reseating all hardware components including cables, CPU, RAM, and GPU
– Inspecting CPU socket for bent pins (none found)
– Reflashing the BIOS (via supported procedures)
– Confirming 12V power delivery to the CPU socket with a multimeter

Additional Considerations
Despite these efforts, the problem persists. The absence of diagnostic indicator lights and a unresponsive power button are particularly telling. Here are further steps and considerations: