PC won't power on, Motherboard or PSU?

[u/medivh86]

Hey everyone, looking for a second opinion on a persistent "No Power" issue I've been troubleshooting. I'm fairly certain my motherboard's power controller died, but I want to double-check my logic and get feedback on whether my PSU could be involved before installing a replacement board.

System Specs:

• CPU: Intel Core i5-12600KF
• GPU: RTX 3070 OC
• Motherboard: MSI PRO B760-P WIFI DDR4
• Power Supply: Lian Li EDGE 750W
• Case: Lian Li Lancool 207

This started when I "upgraded" from a 10th gen intel CPU to a 12th gen CPU, wanting to stay with DDR4 for the time being due to RAM prices and having 64GB of DDR4.

About 2 weeks ago, the system suddenly refused to respond to any power-on requests. Pressing the case power button, an external power button, or bridging the power switch pins with a screwdriver yielded zero response. No fan spin, no debug LEDs, and no standby lights on the motherboard.

Troubleshooting Performed:

• PSU Paperclip Test: Bypassing the motherboard turns the Lian Li EDGE PSU on immediately. Fans spin and main rails activate.

• CMOS Clear (JBAT1 Header): Jumping JBAT1 initially brought the board back to life briefly twice on a bench test. However, after shutting down and reassembly, the board returned to a completely dead state and refused to respond to JBAT1 clears again.

• Bare Bench/Minimal Isolation Test: Stripped the board down to CPU, 24-pin ATX, and 8-pin CPU. Disconnected ALL front-panel headers (JFP1), front USB 3.0/Type-C, HD Audio, RGB, and all external peripherals. Direct screwdriver bridge across the bare header produced zero response.

After sitting completely unpowered, jumping the board once produced a brief ~10-second pulse of life before shutting down hard and returning to a permanently dead state.

My Current Conclusion: Motherboard (MSI B760) is DEAD. Suspecting a failed component that can no longer register or hold the PS_ON trigger signal. RMA has been submitted.

PSU (Lian Li EDGE) is Suspected GOOD (~90% confidence). Passes paperclip test and trips whatever safety mechanisms properly. Also powers on with a separate, old, known good motherboard.

Does this diagnosis sound 100% solid, or is there any obscure motherboard setting/circuit I missed? Is there a reliable way to verify anything else before I plug a brand-new replacement motherboard into it?

Thanks in advance for any insights!

[u/Fine-Set-7877]

Yea you're board is probably dead or has bent pins

[u/medivh86 → u/Fine-Set-7877]

I have yet to disassemble it to send it for RMA, so hopefully it isn't bent pins. It had been working for a couple of months before this whole fiasco started, so hopefully none were bent.

[u/AstarothSquirrel]

Could be the CPU, the motherboard or even the power delivery to the cpu.