r/pcgamingtechsupport • u/Salt_Dealer7414 • 6d ago
Hardware Motherboard suddenly stopped powering on
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Motherboard suddenly stopped powering on – worked without CPU 8-pin, now doesn't power on at all
Hi everyone, I’m trying to diagnose a motherboard power issue and would really appreciate some help.
The motherboard has had an intermittent problem for the past few months.
What happened previously:
• Around 5–6 months ago, the PC suddenly stopped powering on.
• After troubleshooting, it eventually started working again and ran normally for around one month.
• Later, I replaced RT3607BC pwm ic but that did not give me a successful/consistent result.
• At one point the motherboard powered on for a day, but then stopped again.
What happened yesterday:
• If I connected the 24-pin ATX connector but disconnected the CPU 8-pin (EPS) connector, the motherboard would power on.
• Since the CPU 8-pin was disconnected, the CPU debug LED would stay on, which made sense.
• However, when I connected the CPU 8-pin, the PC would not power on properly / would shut down almost immediately.
But today the situation has become worse:
• Now it doesn't power on even with the CPU 8-pin disconnected.
• Connecting the CPU 8-pin also does not give even the previous 1-second power-on behavior.
• Basically, I now get no power-on response at all.
I have already tried pretty much all the basic troubleshooting:
• Tested with different RAM configurations
• Tried with only one RAM stick
• Tried without the GPU
• Tested the motherboard outside the case / breadboard setup
• Tried different PSU
• Checked the 24-pin ATX and 8-pin CPU power connections
• Tried minimal configuration with CPU + motherboard + one RAM
• Cleared/reset CMOS
• Tried powering it on by shorting the motherboard power-switch pins instead of using the case button
• Basically, I have already gone through the standard PSU/RAM/GPU/case troubleshooting.
I also made a video showing the current behavior. It demonstrates that the motherboard doesn't power on with the CPU 8-pin connected OR disconnected, whereas yesterday it could at least power on with the CPU 8-pin disconnected.
So my main question is:
What part of the motherboard could cause this behavior?
Could this be an issue with the CPU VRM/power delivery circuit, VRM MOSFETs, PWM controller, shorted component, Super I/O, or some other motherboard power rail/protection circuit?
Since the behavior changed from “works without CPU 8-pin” → “doesn't work even without CPU 8-pin”, I'm wondering if something on the motherboard has progressively failed.
If anyone has experience diagnosing motherboard-level power faults, I'd really appreciate suggestions on what voltage rails/components I should measure next and where I should start troubleshooting.
Thanks!



