Question Optiplex 9020 Power Off Issue

[Casomme]

Hi,
My optiplex 9020 MT (i7 4770) is having an issue where it will not power down when windows shuts down or when entering sleep mode, in both cases the cpu and rear case fan continue to spin. If I leave the CMOS battery in it will start up once but will not post again after a reset or shut down until I take out the CMOS battery again.

I have tried all the below with no luck:
CMOS Battery out
New CMOS Battery
Updated BIOS to latest version
Unplug all connectors and reconnect
New PSU
multiple types of ram in various DIMMS

Could this be a jumper issue or another issue with the motherboard? I think I have narrowed it down to the motherboard but am not too familiar with diagnosing physical motherboard issues.
Any help would be greatly appreciated

 

[Lutfij]

With all things stated about the prebuilt OptiPlex, did you perform any modifications to the build(apart from the PSU)? Might want to list the make and model of the PSU as well. You should also list the sticks of ram you have to work with and how they're loaded onto the ram slots.

 

[Casomme]

I changed the PSU to a corsair vs450 with 8 pin adapter. Works fine with another optiplex I have. I switched back to the Dell PSU and it does the same thing.

I tried Samsung and Hynix 4gb Ram sticks, I have tried a single stick in all DIMM slots but only really works properly in DIMM 1. Ram all works fine in bios and system information settings with all 4 DIMM slots in use.

Hardware Manual:
https://topics-cdn.dell.com/pdf/optiplex-9020-desktop_owners-manual2_en-us.pdf

I should also add I have gone through the BIOS settings and I can't see any default settings that would make the PC turn on when powered, they are all disabled.