[SOLVED] Mobo powers on without CPU, doesn’t with it

Nov 4, 2019
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Hey all! :)

I could use some help with a new build (specs below). Doesn’t turn on only when CPU power is connected. Tried the steps in the sticky.

ATX power + no CPU power = mobo is powered, all fans and leds are on, stays that way; doesn’t post of course

ATX power + CPU power = mobo powers on for a sec, then off, then on again, etc.; will do this with either 4pin or 8pin CPU connectors in, or both

I’ve re-seated CPU and RAM to no effect. CPU fan connected or not makes no diff. Discrete GPU or not also makes no diff. No thermal paste on CPU heatsink.

Any ideas? I appreciate the help! :D

MSI MPG Z390 Pro Carbon
i9700k never OCed w/ Thermaltake Gravity i2
EVGA 1000 GQ or Corsair RM850 (same result)
16GB DDR4
2x Zotac GTX 1080 Mini
M2 Samsung 970 EVO
Antec NX400
 

SwetishBus0964

Reputable
Aug 12, 2015
40
0
4,530
1
I had a similiar issue with one of my other MOBOs. I could turn the Computer on without the CPU plugged in, but as soon as it did, it shut off nearly instantly. I found my issue to have been a connecting piece or whatever. I had to examine the back before i found a very small black/brown coloration around where the CPU power plugs into. It is possible this happened to you as well?

I would check just to be sure. If it is the issue then you could return/get a new motherboard. This is just based off my experience. But i would definitely look at the back near the power connector and check for any discoloration
 

cin19

Titan
Moderator
Hey all! :)

I could use some help with a new build (specs below). Doesn’t turn on only when CPU power is connected. Tried the steps in the sticky.

ATX power + no CPU power = mobo is powered, all fans and leds are on, stays that way; doesn’t post of course

ATX power + CPU power = mobo powers on for a sec, then off, then on again, etc.; will do this with either 4pin or 8pin CPU connectors in, or both

I’ve re-seated CPU and RAM to no effect. CPU fan connected or not makes no diff. Discrete GPU or not also makes no diff. No thermal paste on CPU heatsink.

Any ideas? I appreciate the help! :D

MSI MPG Z390 Pro Carbon
i9700k never OCed w/ Thermaltake Gravity i2
EVGA 1000 GQ or Corsair RM850 (same result)
16GB DDR4
2x Zotac GTX 1080 Mini
M2 Samsung 970 EVO
Antec NX400
No thermal paste on CPU heatsink? you can't do that, which will kill the cpu. You have to apply it, that why the pc turns on for second, then turns off, because the MB has the protection feature.
 
Nov 4, 2019
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LOL the vid is hilarious! I forgot to apply the paste because usually I use the stock cooler that already has it, but not in this case. Now I’ve applied it and reseated the cooler. Same result as before.
 
As you have two PSUs, when trying the other PSU, were any of the old PSUs modular cables then used with the substitute PSU, or, did you properly use all new modular cables as required? (All bets are off if cables mixed)

Remove both GPUs, drop to one RAM stick in required 2nd slot and see if you can get a POST with a single RAM stick connected to mainboard's HDMI out, since CPU supports integrated video out...

(My fear is that, if cables were mixed, whatever the original problem might have been might not be the only issue now. Hopefully a baseless concern!)
 

SwetishBus0964

Reputable
Aug 12, 2015
40
0
4,530
1
I had a similiar issue with one of my other MOBOs. I could turn the Computer on without the CPU plugged in, but as soon as it did, it shut off nearly instantly. I found my issue to have been a connecting piece or whatever. I had to examine the back before i found a very small black/brown coloration around where the CPU power plugs into. It is possible this happened to you as well?

I would check just to be sure. If it is the issue then you could return/get a new motherboard. This is just based off my experience. But i would definitely look at the back near the power connector and check for any discoloration
 
Nov 4, 2019
3
0
10
0
Do you try to clear the CMOS first, then boot the PC?
I do this whenever I reseat the CPU. No change. :(

Remove both GPUs, drop to one RAM stick in required 2nd slot and see if you can get a POST with a single RAM stick connected to mainboard's HDMI out, since CPU supports integrated video out...
Cables weren’t mixed, thankfully. I can’t get a POST even with a single RAM stick. For that matter, the mobo doesn’t even beep when I power on with no RAM at all.

But i would definitely look at the back near the power connector and check for any discoloration
Thank you for this. There’s definitely a smudge behind it, though I wouldn’t call it a discoloration. Regardless, it seems like I might have a bad board...
 

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