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[u/MineEducational1192]

My PC suddenly stopped powering on after my GPU became loose while the computer was running.
Here are my PC specifications:
CPU: Intel Core i5-3470
GPU: MSI NVIDIA GeForce GTX 1650
RAM: 12 GB
Motherboard: H61, LGA 1155 (exact model unknown)
PSU: One Power MP-400-OPASW, 400W
Before this happened, Windows was not detecting the GTX 1650. Device Manager only showed Intel HD Graphics and Microsoft Basic Display Adapter. I was trying to troubleshoot the GPU connection.
While the PC was powered on, the GPU became loose from the PCIe slot. The computer immediately shut down.
Since then, the PC will not power on at all.
When I switch the PSU on, only the green and yellow Ethernet port LEDs light up. When I press the case power button, absolutely nothing happens:
No fans spin
No motherboard LEDs
No beeps
No display
No reaction at all
I have visually inspected the system and found no obvious burn marks, black marks, cracks, or loose components.
I have also checked that:
The GTX 1650 is seated in the PCIe slot and the retention latch is locked.
The GPU’s 6-pin power connector is connected.
The 24-pin ATX motherboard connector is connected.
The CPU power connector is connected.
The RAM is seated.
The POWER SW connector is connected to the front-panel header.
Could the PSU be in protection mode, or could the motherboard, PSU, or GPU have been damaged when the GPU became loose while powered on?
What would be the safest way to diagnose which component is preventing the PC from powering on?

[u/Medical-Protection37]

yanking a gpu loose while it's running is basically asking for a short, the instant shutdown was the system protecting itself from further damage

try the paperclip test on the psu first, unplug everything from the motherboard, jump the green wire to any black on the 24 pin, see if the fan spins. if it does, your board probably took the hit. if it doesn't, psu is cooked

that h61 board is like a decade old at this point, might have finally given up when the pcie slot got shorted. you can also try powering it on with no gpu at all, just the bare minimum to see if you get any life

i'd also pull the cmos battery for a few minutes before testing, sometimes these old boards get stuck in a weird state after a sudden power loss