[SOLVED] HELP! Installed new CPU and PC will not boot with 8-pin CPU power cable

[6henny]

I was having overheating issues after 3 years of solid running with no problems. I boiled it down to a failed h100i cooler pump. (which started making whining noises) I swapped my i5-6600k for an i5-9400 just to use the stock cooler for now, and bought a GTX 1660S to replace my RX480 all for <Mod Edit> and giggles no issues with CPU or GPU sold them both. When i installed the new CPU and tried to boot it up, everything came on for 1 second and then shut off.( It only repeats this when I cycle the power switch on the PSU and try to power it on again.) The only way I can get the PC to stay on is if I unplug the 8-pin CPU power cable. Everything runs like normal except the CPU is unplugged. I cannot figure out why I cannot get it to boot. The PC booted and ran fine 2 days ago aside from the cooling issue. Brand new CPU. Brand new GPU. Board is an MSI Krait Gaming 3X, running Corsair CX 750M PSU, Ballistix DDR4

 

[kwikgta]

Do you have another PSU to try?

 

[rgd1101]

did you change the motherboard?
motherboard that work with 6th gen does NOT work for 9th gen cpu

is that MSI Krait Gaming 3X the Z170A
yup that doesn't work with 9th gen

 

[XxDarkMario20xX]

MSI Krait Gaming 3X, dose not surrport your CPU you need to find an motherboard that surrports 9 gen that why its not booting!

 

[DSzymborski]

Yup, pretty easy one. Your new motherboard can only run Skylake and Kaby Lake CPUs. You absolutely can not run an i5-9400 on any Z170 motherboard.

 

[6henny]

thanks all for the replies. it’s the old motherboard from the old CPU. After yanking my hair out I realize it’s the board compatibility with 9th gen. i ruled that out because I saw that it works on some forum. I will try a new board tomorrow. any recommendations?