💡 Overview

The Power Supply Unit (PSU) delivers power to every component in your computer. A failing PSU can mimic symptoms of failing motherboards, CPUs, or even RAM — making it one of the hardest components to isolate without proper tools.

Common symptoms of PSU issues include:

• System not powering on
• Random reboots or shutdowns
• No POST or intermittent power
• Burning smell, clicking, or coil whine

🧰 Tools You’ll Need

• 🔌 Spare Known-Good PSU (if available)
• 🔧 Multimeter (for voltage testing)
• 🧪 PSU Tester (optional but useful)
• 🔄 Paperclip Test (quick jump-start)
• 📈 OCCT or HWiNFO (for software-level PSU sensor monitoring)

🪜 Step-by-Step Diagnostic Process

1. ✅ Visual & Smell Check
   • Look for blown capacitors, melted cables, or discolored connectors.
   • Smell the PSU exhaust area — a burnt smell is a red flag.
2. 🔌 Paperclip Test (Jump Start PSU)
   • Unplug the PSU.
   • Bridge the green wire and any black wire on the 24-pin connector with a paperclip.
   • Plug the PSU back in and turn it on.
   • If the fan doesn’t spin, the PSU is dead or in protection mode.
3. 🔎 Multimeter Voltage Check
   • Test voltage on:
     • +3.3V rail (orange)
     • +5V rail (red)
     • +12V rail (yellow)
   • Acceptable range: ±5% tolerance (e.g., 12V rail should be between 11.4V–12.6V)
4. 🧪 Try PSU in Another System (If Possible)
   • If the PSU powers another system stably, the issue may be elsewhere.
5. 🔄 Try Known-Good PSU in Current System
   • Swap in a known-good PSU to rule out power as the cause.
6. 💻 Check Software Sensors
   • Use HWiNFO, Open Hardware Monitor, or OCCT to log voltage dips under load.
   • Sudden drops in +12V, +5V, or +3.3V lines indicate instability.

📉 Example Symptoms and What They Mean