CPU and Motherboard issue

Steve Rose · 25 Feb 2019 at 13:29

Hi All,
Fist of all apologies if this is posted in the wrong section!
I have an issue with my new build/upgrade. I would like to use an i7 8700k in an MSI Z390 A PRO with 16GB RAM and an 1080Ti. My PSU covers 750W.
After building it together when turned on,the system goes into a power up loop. Checked the motherboard if it touches the housing but it is clear, removed all components and took out the mobo from the case. When taking out the CPU the board powers up, when inserting the CPU back and starting it up the loop's there again.
Both components are clean and have no visible damage also the board should support gen 8th CPUs. I haven't tried to CMOS the motherboard yet, first I thought I get some advise

What are your thoughts? Anyone has encountered anything similar?
Thanks in advance for the help!

Steve

LuckyBenski · 25 Feb 2019 at 17:45

A few pointers -

Clearing CMOS is no big deal, especially if you haven't configured anything yet. Be sure to turn off at the wall/power supply and remove the battery before shorting the jumper.

I wouldn't expect much out of a motherboard with no CPU, so wouldn't bother trying to power up that way. Others may disagree though

I would (initially, and certainly at this stage) try booting with minimal peripherals. No GPU, and just one RAM stick. I'd also try this outside the case to rule out shorting. The motherboard box makes a good desk (don't sit it on the ESD bag, that's conductive).

With that out the way I'll ask some basics - are all power cables plugged into the motherboard i.e. ATX EPS 4/8pin connectors.

Edit: sorry, i see you've done most of this. Are you leaving one RAM stick in? Tried changing the slot it's in?

Steve Rose · 25 Feb 2019 at 18:11

Hey,
I was just checking if the board gets enough power or is faulty that is why I turned it on by itself. The problem is that once the CPU is inserted into the board, it does not matter what else I have plugged in as it won't start up. It gets power for maybe a second, the fans start to spin, the LED on the board lights up and then nothing. After 2 seconds this happens again - so I did remove the CPU to see what happens and the board was functioning with the fans spinning all the way and the LED was constantly on. This is why I think that it is maybe a power transfer problem on the board or the CPU socket has some damage that is not visible by the eye?
I will do the CMOS and post the update.

pastymuncher · 25 Feb 2019 at 19:05

What make and model is that 750w psu? Do you have both the 24pin and 8 pin power leads connected? Don't plug anything into the 6 pin socket.

Steve Rose · 25 Feb 2019 at 19:56

It's an Antec True Power Classic 80 Plus Gold - this is from my previous build, both the mobo and the CPU are new.
Yes both were connected and the GPU socket was not plugged in. Tried it with 4 and with 8 pins as well as the board can be OC'd.

Steve Rose · 26 Feb 2019 at 18:20

Hey guys,
I did a CMOS on the mobo and also gotten a new PSU and now the board is powering up while the CPU is inserted. I don't know whether the reset or the PSU did the job, but I am happy now