RMAd Mobo and CPU, CPU diagnostic light always on, no BIOS/boot loop

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  1. Posts : 7
    Windows 10 Pro 20H2
       #1

    RMAd Mobo and CPU, CPU diagnostic light always on, no BIOS/boot loop


    Hi all, first time poster. Recently I bought upgrade parts for my existing computer: A Ryzen 9 3900X and a Gigabyte X570 Aorus Pro Wifi. Im switching from Intel to AMD. I got the motherboard used, and the 3900X new, both from B&H. I install all the parts, and lo and behold, I cant get anything. The CPU diagnostic light is lit, and there is no output from the card. After troubleshooting, I figured it was a defective used board and returned the board back to B&H. A week later, I got a new board back. Same issue. Im about to return both board and CPU when I managed to use the Q-Flash feature on my motherboard and update to the latest bios. I return the CPU only. Today, I get the replacement CPU. Same issue again. No matter what, as long as the CPU is inserted and power is on, the CPU diagnostic light is on. After starting, the front panel buttons no longer work (power, reset), and I have to turn off the PSU to shut it down. Fans spin, but I cannot get past the CPU diagnostic light at all. There is a chipset fan that comes on every startup, but is supposed to stop after successful POST. My chipset fan stays running at full speed. The behavior is the same from one mobo to next, and one CPU to the next. Ive tried many different configurations.

    Completely bare bones (everything out), with only CPU and power. CPU light is on.
    Dual RAM, single RAM, single RAM tried in every slot. CPU light is on.
    Tried different PCIe slots for the GPU and removing the GPU. CPU light is on.
    Cleared the CMOS. CPU light is on.
    Tried without a cooler briefly to ensure mounting pressure wasnt too high. CPU light is on.
    Tested PSU with paperclip test. PSU Working.
    Its sitting on a cardboard box right now, with the PSU also removed from the case. CPU light is on.
    Flashed updated bios. CPU light is still on.
    M.2 and SATA slots are all empty.
    I swear Ive completely exhausted my options and Im about to give up. Any advice?

    I should note that when I tried it without the cooler, I was feeling the surface of the CPU lid and it was getting warm. So something was definitely happening inside there. But alas, the light stayed lit, even after allowing 10 minutes for the computer to run (because I read that new motherboards might need more time to index RAM).

    Specs are:
    EVGA Supernova G2 750 Gold
    Ryzen 9 3900X
    Gigabyte X570 Aorus Pro Wifi (REV1.1, then REV1.2)
    Micron (Ballistix brand) DDR4-2666, 2x 8GB, BLS8G4D26BFSEK.8FD
    MSI R9 390, using DVI output
    Windows version would be Windows 10 Pro 20H2, if only I could get into my computer first
      My Computer


  2. Posts : 18,403
    Windows 11 Pro
       #2

    Is the CPU power connector plugged into the motherboard? Normally a 4 or 6 pin connector in the upper left corner.
      My Computer


  3. Posts : 7
    Windows 10 Pro 20H2
    Thread Starter
       #3

    NavyLCDR said:
    Is the CPU power connector plugged into the motherboard? Normally a 4 or 6 pin connector in the upper left corner.
    Yessiree, my example is an 8pin+4. I made sure both cables are snapped in, on the mobo and modular PSU ends.
      My Computer


  4. Posts : 22,685
    Win 10 Home ♦♦♦19045.4046 (x64) [22H2]
       #4

    @sukiyakis


    Things to check...
    Make sure the BIOS is set to defaults.
    Make sure the thermal compound is does right and is not TOO much.
    Make sure no pins are bent.
    Make sure the triangles are lined up on the CPU and the CPU socket.

    -image1.png






    Make sure the CPU fan is plugged into the CPU_FAN connector on the motherboard.

    -image1.png






    I can't find the RAM you listed on the Memory QVL list from Gigabyte. (may or may not be an issue)
      My Computer


  5. Posts : 7
    Windows 10 Pro 20H2
    Thread Starter
       #5

    Ghot said:
    @sukiyakis


    Things to check...
    Make sure the BIOS is set to defaults.
    Make sure the thermal compound is does right and is not TOO much.
    Make sure no pins are bent.
    Make sure the triangles are lined up on the CPU and the CPU socket.

    <img>

    Make sure the CPU fan is plugged into the CPU_FAN connector on the motherboard.

    <img>
    Done, done, and done

    I can't find the RAM you listed on the Memory QVL list from Gigabyte.
    This is worth looking into more. Thank you.
      My Computer


  6. Posts : 22,685
    Win 10 Home ♦♦♦19045.4046 (x64) [22H2]
       #6

    sukiyakis said:
    Done, done, and done



    This is worth looking into more. Thank you.



    If there is too much thermal compound and it leaks out, it can run down into the CPU socket and cause problems.
      My Computer


  7. Posts : 7
    Windows 10 Pro 20H2
    Thread Starter
       #7

    Ghot said:
    If there is too much thermal compound and it leaks out, it can run down into the CPU socket and cause problems.
    Gotcha, mine's a pretty even spread, nothing that stands out as overdone
      My Computer


  8. Posts : 22,685
    Win 10 Home ♦♦♦19045.4046 (x64) [22H2]
       #8

    sukiyakis said:
    Gotcha, mine's a pretty even spread, nothing that stands out as overdone

    On the 3900X you should probably use the X method.
    Every time you remove the CPU cooler you have to clean the thermal compound off, and re-apply a new amount.





    -image1.png







    Contact Us - GIGABYTE U.S.A.
      My Computer


  9. Posts : 7,829
    Windows 11 Pro 64 bit
       #9

    I note the PSU passes the paperclip test but I would also check the correct voltage is being output on all power lines - or substitute another PSU
      My Computers


  10. Posts : 7
    Windows 10 Pro 20H2
    Thread Starter
       #10

    Steve C said:
    I note the PSU passes the paperclip test but I would also check the correct voltage is being output on all power lines - or substitute another PSU
    This might be my excuse to finally get a multimeter. However this PSU has been used for my past two builds without issue, but I understand something catastrophic still might have happened

    - - - Updated - - -

    I'm gonna test out my old motherboard and CPU which I know is working, just to confirm it's not a PSU problem.
      My Computer


 

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