Question New AMD 3900X build won't POST

[EddieQ8]

Hello,
I've recently completed building a new AMD gaming rig using the following components;

-CPU: AMD 9 3900X RYZEN CPU Processor w/stock fan.
-MOBO: Asus X570E ROG Strix ATX
-SSD: SAMSUNG 1TB SSD 970 EVO Plus, NVMe M.2 Client
-RAM: GSKILL 4266MHz 16GB RAM RGB, TridentZ Series, PC4 34100
-GPU: Asus 8gb Rog Strix RX VEGA64 OC edition
-PSU: Corsair HX850i 850W PSU, 850 Watt, 80+ Platinum

Long story short, PC won't start. The RGB's on the mobo light up fine, as do the two LED's on the GPU, but that's it. No fan spin up, no screen on, absolutely quiet. I plugged in a USB-powered LED light in all the external USB ports (front & rear) and the light works fine, but no POSTíng at all.

I tested the PSU using the on-board self-test button and the fan spun quietly, so that - in addition to the RBG & LED lights mentioned earlier- proves to me that there is nothing wrong with the PSU.

I removed all the components & installed them onto a similar Mobo but with less flashy specs (Asus X570F), same story.
I quadruple-checked the leads, connectors, plugs, wires, standoffs, everything seems to be ok, but it still wont POST.
I plugged in a single RAM slot instead of the two, no POST.
I plugged in the HDMI cable into the Mobo's slot as well as the GPU's slot, no POST.
I tried using one SSD instead of two, no POST.
I tried resetting the BIOS, CMOS, BIOS update, battery removal, no POST.

I've followed online recommendations and advice & bread-boarded the setup, still no POST.

I'm beginning to think that I've been working with a faulty CPU to begin with. But as long as the rig won't POST, there is no way for me to know for sure, without purchasing another CPU & installing it again.

I would appreciate any help or insights anyone can provide.

Thanks in advance.
Ed.

 

[Ancient_1]

I would guess it is your PS. The led lights lust need the standby power to work not the psu to actually function. The cpu is the last thing I would think. I don't know what the psu test you did entails but that is my best guess.

Here is a shot of my system with a bad PS. it was so bad it killed 3 HDs and a 16g stick of ram and never showed any sign of life when I hit the power switch.

And here is one with the old PS installed as you can see the fans spin and diagnostic lights are working (the amber light indicates memory problem) and the Qled shows 0d which also indicated memory.

 

[gingerrankin]

if I'm not mistaken your mobo displays a two-position q-code with a status code. I'm right? What code appears?

 

[EddieQ8]

Hello,

Thanks so much for replying.

Unfortunately, neither motherboard displayed ANY code of any kind, just the RGB lights. You will note that I tried using two mobo's, an E and an F and the results are the same...nothing!

When i switched to the lower-spec'ed Mobo, as i mentioned, the only way I could tell if the power was actually on - aside from switching on the PSU from the rear - was to plug in a USB-powered light. That, and the two white LED's on the GPU, right on top of where the power cables connect.

On that note, and as part of my troubleshooting, as this mobo type require two EATX power connectors to be plugged at the top, (labelled as 8-pin EATX12V_1 and 4-pin EATX12V_2 in the manual and the PCB) into the i tried to unplug the 4-pin connector from the top of the mobo so that only the 8-pin connector was attached, and a red LED light showed up atop the connector. It disappeared when I plugged it in again.

When I described the PSU's self-test, I'm talking about this feature where there's a 'test' button at the back/inside of the PSU (pictured here). The PSU manual says that when it's depressed, the PSU's fan should spin and that's how you know that your PSU is working normally. At this point, this is my evidence that the PSU isn't at fault.

I have not tried the paperclip test yet, i'm not so sure I'm ready to poke into electrical wires with metal objects just yet. Admittedly, this is only my second build, and my first was an Intel machine over 7 years ago.

Should I?
On the other hand, would a faulty CPU stop a motherboard from POST'ing?

I appreciate you taking the time to help me out, and I hope you bear with me.

Regards,
M.

 

[Ancient_1]

You don't need both the 4 pin and 8 pin plugged in. Just the 8 is p[plenty. I have the same mother board with a 3950 and runs fine with just the 8. I am pretty sure that the board should come to life even without a cpu even tho I doubt would post You would get one of the leds on the top right of the board showing a different color than the amber mine is showing for the faulty memory that would indicate a cpu (I don't remember the color for a cpu fault).

 

[EddieQ8]

Hello, thanks for replying,

So, even if the CPU was faulty/uninstalled, the motherboard should come to life somehow? Case fans & all?

 

[RodroX]

Hello, have you tried to turn on the PC with only CPU+1 stick of RAM; yes you read right no GPU, no HDD, no SSD, no case fans, no RGD lights, no keyboard, no mouse, no printer, nothing. In fact unplug the front case USB and sound ports too. Unplugg everything, leave the CPU + 1 RAM stick and see what it does (you can try the other stick of RAM too and all the slots availables).

NOTE: Don't plug the display on the back of the motherboard your CPU does not come with an integrated GPU.

If everything seems the same but, now the CPU fan spin, I would next turn the power OFF and try to plug in a GPU (if you have an extra GPU you can try this is the time, maybe something less power hungry than your VEGA 64).

Cheers

 

[EddieQ8]

Hello,

I've removed everything from the case again, removed the motherboard & placed it on it's box, kept only one stick of RAM as well as the CPU & it's fan installed & plugged in, connected the power cables to the PSU (which I've also removed from the case), switched on the PSU, and......nothing!

Tried using other RAM slots, nothing, Tried a different stick of RAM, nothing.

I plugged in the USB light into one of the rear USB slots of the motherboard and it lit up, but that's about it.

I even tried touching the two power pins with a screwdriver to emulate the power on"" switch, nothing.

My next shot is to try out another PSU, but if that doesn't work, what's next?

 

[EddieQ8]

Hello,

HELP!! I've tried a brand new PSU and bread boarded the whole setup - on two different Motherboards - and I still wont get any activity (aside from a few RGB lights on the ROG STRX-E).

No POSTing, no fan spin, No error code, no LED indicators, and nothing... it's just dead.

I've now gone through two different motherboards and two different PSU's at this point...tried all sorts of combinations of peripheral setups, both in and out of the case...the the results are the same....absolutely nothing.

I'm thinking of getting a less-expensive CPU to prove that my first one was faulty, unless there's a test that I don't know about that would tell me whether or not it's dead.

Appreciate any insights anyone has.

Kind Regards,

 

[RodroX]

If you tried two diferent motherboards and PSUs, and perhaps you also tried diferent RAM, then it seems all fingers point to the CPU yeah.