Question Replacement power supply startup issues

Feb 26, 2023
Hey all! I just decided to upgrade my dying PSU. On my dying PSU my pc ran great once it turned on, but it does take anywhere from 5 to 20 power button presses to turn on.

The dying power supply is a Gigabyte P750GM.
This morning after successfully turning my pc on, i decided to go ahead and install a replacement PSU i purchased a week earlier.

Replacement PSU is a ROG THOR 850W Platinum fully modular.

After replacing and connecting all the old cables with the new cables from the PSU, i hit the power button, which now works flawlessly and instantly powers my PSU, my computer roars to life and sounds healthy with all fans working on components. But bios doesnt post and it remains a black screen. The red CPU light on the motherboard is a solid red. Ive unplugged and replugged the cables, tried every combination of ram slots with no difference on startup. Sounds super healthy, but no bios posting, this build is two years old, and restating again, the build was working when i decided to replace the dying PSU. Any thoughts and suggestions would be much appreciated!!!

CPU: Ryzen 7 5800X
Motherboard: Gigabyte X570 Aorus Ultra
GPU: GTX 1080 Ti
Ram: Gskill Trident Z 3600 DDR4
Sounds to me like something is being overlooked. Make certain to triple check EVERYTHING at the following link including making absolutely certain you're fully seating the EPS, ATX and PCIe cables to the motherboard, CPU auxiliary power and graphics card, and that none of the other cables to the drives or motherboard that do not come from the power supply have been accidentally bumped or knocked free.

If that fails to resolve anything then I'd at least attempt to do a hard reset.

BIOS Hard Reset procedure

Power off the unit, switch the PSU off and unplug the PSU cord from either the wall or the power supply.

Remove the motherboard CMOS battery for about three to five minutes. In some cases it may be necessary to remove the graphics card to access the CMOS battery.

During that five minutes while the CMOS battery is out of the motherboard, press the power button on the case, continuously, for 15-30 seconds, in order to deplete any residual charge that might be present in the CMOS circuit. After the five minutes is up, reinstall the CMOS battery making sure to insert it with the correct side up just as it came out.

If you had to remove the graphics card you can now reinstall it, but remember to reconnect your power cables if there were any attached to it as well as your display cable.

Now, plug the power supply cable back in, switch the PSU back on and power up the system. It should display the POST screen and the options to enter CMOS/BIOS setup. Enter the bios setup program and reconfigure the boot settings for either the Windows boot manager or for legacy systems, the drive your OS is installed on if necessary.

Save settings and exit. If the system will POST and boot then you can move forward from there including going back into the bios and configuring any other custom settings you may need to configure such as Memory XMP, A-XMP or D.O.C.P profile settings, custom fan profile settings or other specific settings you may have previously had configured that were wiped out by resetting the CMOS.

In some cases it may be necessary when you go into the BIOS after a reset, to load the Optimal default or Default values and then save settings, to actually get the BIOS to fully reset and force recreation of the hardware tables.

And if that fails to resolve the issue you will want to begin bench testing.

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