B450 3800X PC sometimes doesn't post

[dan_bodz]

Hi all,

I'm having an issue whereby my PC sometimes doesn't post however when it does post the system works perfectly. It fails to post after I shut it down and do not leave it for 30mins-1h+ before turning it back on again. If I leave it for a while before powering it on it will 100% work first time. My gut feeling is that this is to do with capacitors needing to discharge before it is stable to boot or something similar.

 

I have some backlight LEDs on my motherboard which under ideal circumstances are white for a few seconds and then remain red for the remainder of the time when my PC is on. When it fails to post, the backlight LEDs stay white and never turn red which leads me to believe that some kind of initial check is failing. I have some debug LEDs (CPU, DRAM, VGA and BOOT) of which a seemingly random assortment of CPU, DRAM and VGA light up permanently when it fails to post. Additionally the fans are all stuck at 100% usage and there is no video output.

 

Steps I have tried already to fix the issue:

• Update BIOS to latest version
• Clear CMOS several times before and after BIOS update
• Unplugging of all SATA and USB devices
• Running several passes of Memtest86 with 0 errors
• Unplugging the reset switch (suggested elsewhere)
• Turned off fast startup in Win10
• Swapping to different combinations of RAM slot(s)
• Ensuring all power connectors are plugged in properly
• Disable XMP profile

Specs are as follows:

• 3800X (new)
• MSI B450 Tommahawx MAX (new)
• HyperX Fury DDR4 16GB 3200MHz (new)
• GTX 1060 (a few years old)
• 600W PSU (a few years old)
• ASUS PCI wifi card

Any help would be very much appreciated; it seems as though the only consistency is that if I leave the PC powered off for some time the first boot attempt will always work first time. If I can't fix it soon I may RMA the motherboard as this shouldn't happen with brand new components.

Many thanks.

[Slamburger]

Have you tried disconnecting every device except what's necessary? Like leaving only the motherboard, harddrive, one stick of ram, and the CPU as the only devices connected. This will help you isolate your issue.

[dan_bodz]

2 hours ago, Slamburger said:

Have you tried disconnecting every device except what's necessary? Like leaving only the motherboard, harddrive, one stick of ram, and the CPU as the only devices connected. This will help you isolate your issue.

Yup just tried with nothing except PSU, CPU, motherboard and every possible combination of ram :(