Question No Power/System not starting unless CPU power cable is disconnected from the Motherboard

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Agoniyz

Agoniyz

Dec 12, 2024
10
3
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Hello everyone,

I‘m slowly getting desperate, i‘ve spent countless hours searching the web and trying to find out what caused this.

I recently exchanged my motherboard for a new one (MSI MPG B550 Gaming plus AM4).

CPU is Ryzen 7 5800x

After the install - everything ran like butter and the PC was working well fpr about 1-2 days.

Yesterday I pressed the PW button and nothing happend, no lights, no fans nothing.

first I thought the PSU was faulty but I tested it with a paper clip and I even plugged it on another motherboard with the same CPU.

Worked fine.

So this is clearly a MOBO problem…thing is…itd brand new and it worked until it suddenly didnt.

Only thing I could notice when checking the cables was ou the little 4pin connector attached to the 20pin connector (AC power) not being insterted properly this whole time.

Unsure if that caused the Motherboard to fail…

Like the title says : Mobo runs aswell but ONLY when the 2x4 pin CPU power isnt connected
 
Agoniyz said:
Hello everyone,

I‘m slowly getting desperate, i‘ve spent countless hours searching the web and trying to find out what caused this.

I recently exchanged my motherboard for a new one (MSI MPG B550 Gaming plus AM4).

CPU is Ryzen 7 5800x

After the install - everything ran like butter and the PC was working well fpr about 1-2 days.

Yesterday I pressed the PW button and nothing happend, no lights, no fans nothing.

first I thought the PSU was faulty but I tested it with a paper clip and I even plugged it on another motherboard with the same CPU.

Worked fine.

So this is clearly a MOBO problem…thing is…itd brand new and it worked until it suddenly didnt.

Only thing I could notice when checking the cables was ou the little 4pin connector attached to the 20pin connector (AC power) not being insterted properly this whole time.

Unsure if that caused the Motherboard to fail…

Like the title says : Mobo runs aswell but ONLY when the 2x4 pin CPU power isnt connected
Click to expand...
Id like to add: the white DEBUG LED is on (cpu) when the mobo seems like its running
 
Check the CPU for bent pins. This is a weird "one or the other" scenario. I'd imagine since you just bought a new board you'd be able to return it or have it repaired, but I would diag this some more. Are you getting any post beeps?
 
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Dashhh said:
Check the CPU for bent pins. This is a weird "one or the other" scenario. I'd imagine since you just bought a new board you'd be able to return it or have it repaired, but I would diag this some more. Are you getting any post beeps?
Click to expand...
Thanks for your help brother,

No beeps no sound, all I get is a 0,5 sec red light from the MOBO.
 
The 4-pin you're referring to, is that from the PSU? If that wasn't installed correctly then my brain goes immediately to an overvoltage issue that could have dinked your CPU or board over the course of the 2 days you had it operational.
 
yes the 4 pin that is part of the ATX main connector. It wasnt clicked in lets say…

Your insight and the fact that everything ran ( CPU too) fine on the old MOBO - kinda confirms that the board is at fault.

Or am I missing something crucial here
 
Well, I don't feel like I have much information to go off of other than your system won't boot when the 4-pin is connected because it wasn't "clicked in let's say..." haha. When your system IS on without the 4-pin, are you able to get any logs or metrics from monitoring software or anything? Have you jumped into any of that?
 
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The system is „on“ (fans spin, led lights flash etc… ) when the 2x4 pin at the top left is disconnected. It doesnt boot obviously haha

That 2x4 pin was connected very fine. It was the 4 pin that is attached to the other 20pins that wasnt fully inserted.

I will try to link some pictures if I can:)
 
Do you happen to have an older CPU in the same chipset from an upgrade or anything? Is your PSU modular to where you can completely disconnect your cables?
 
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I have a Ryzen 5 2600x from my old build and the PSU is not modulr, the cables come with it.

its a bequiet Pure Power 10 600W
 
A few things. Both of those chips are AM4, so test your old CPU in the new board and see if you can boot with that installed. Second, can you list your full system specs? Not that I suspect this of an issue, but the 5800 has a max power draw of over 2 times that of the 2600. Pending your other hardware, a 600w PSU may play into this more than we might suspect. I'm curious at the very least.
 
MSI MPG B550 Gaming Plus
Ryzen 7 5800x
CPU Cooler: Corsair H100 RGB 240mm
2x GB DDR4 RAM Kingston Fury RGB
GTX 1080 MSI AERO
1x Fan at the back
1x Fan at the front
Normally i have a 256gb SATA SSD plugged in and a Toschiba 1TB hard disk.
 
Last edited:
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You're at about 500w with that build, so you have a little headroom as far as power consumption goes. Now, test that other AM4 chip and see if you can boot. If that works, we can at least narrow some things down. If that doesn't work, we'll try some other things.
 
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