Hi all,
 
I have just finished building a new PC and am having a strange issue with my 1200 P2 (around 4 years old).  As soon as I flip the power switch on the PSU the PSU fan starts spinning, once i turn the PC on the fan goes off (Eco mode is on, if i turn it off the fan spins) and seemingly operates normally.  When i shut down the PC from windows the PSU fan will stay spinning.  It will only stop if I flick the switch on the PSU to off.  I have disconnected the 24 pin from the motherboard and used the jumper and everything operated normally.  I was using cable extensions, though i tried with no extension and the same behaviour occured.  The PC appears to be running fine, no strange behaviour)
 
I do have another PSU though due to the cabling set-up it is a major effort to unplug the P2.  Am i able to leave all the cables except the 24 pin plugged into the P2 and components (no power going into the P2) and just plug the 24 pin cable from my spare PSU into the motherboard to see if it shows the same behaviour when i flick the PSU switch or would this damage things?
 
Components are : 3900x, Gigabyte master x570, 2080ti, 32gb ram, 2 nvme drives, 1 hdd, 2 D5 pumps, Aquaero 6 lt, Quadro.
 
Hope the post makes sense.

kwomo
Am i able to leave all the cables except the 24 pin plugged into the P2 and components (no power going into the P2) and just plug the 24 pin cable from my spare PSU into the motherboard to see if it shows the same behaviour when i flick the PSU switch or would this damage things?

 
That's fine..What is your spare PSU, by the way?
 

Thanks for your reply, i'll give that a try later today and see what happens.  It's a Coolermaster MWE 550w gold.

bob16314
Just to be clear, don't use ANY cables from the EVGA unit with the Coolemaster, and vice-versa..But you probably already knew that. 

Yeah I definitely won't be doing that.  Thanks for the reminder though. 

Well, let's not be too hasty in condemning any hardware yet without trying a few things first.

1. Make sure the Mobo BIOS is up-to-date with the latest from your mobo page at Gigabyte, I see there's 5 updates for an X570 Aorus Master since initial release.

2. Enable ErP Mode in the BIOS -> Settings section.

3. Contact Gigabyte Support and see what they say (but my crystal ball tells me they'll say the PSUs you tried are bad).

bob16314
Well, let's not be too hasty in condemning any hardware yet without trying a few things first.

1. Make sure the Mobo BIOS is up-to-date with the latest from your mobo page at Gigabyte, I see there's 5 updates for an X570 Aorus Master since initial release.

2. Enable ErP Mode in the BIOS -> Settings section.

3. Contact Gigabyte Support and see what they say (but my crystal ball tells me they'll say the PSUs you tried are bad).

Hi,
1. I have tried three different BIOS versions today including the most recent with no change to the problem.
2. I have enabled ErP in BIOS and noticed no change in behaviour.  
3. I got a reply back from Gigabyte today.  There only suggestion was to clear the CMOS and try again.   I don't have access to the battery (custom loop) so could only clear the CMOS by the clear CMOS button or by the jumper.  I'm not sure there is any difference in any of the methods, Gigabyte did give me the instructions for the battery method.  They did also note that the behaviour is not normal and to contact the seller if the problem persists.
 
My next plan is to take the loop apart and test the motherboard out of the case with nothing plugged in/installed other than the 24 pin cable.  Probably won't get around to doing that until the weekend though so any other suggestions would be highly appreciated.
 
Thanks for all the suggestions so far, appreciate it greatly.

Check the MB manual ... usually the battery does Not have to be removed if designed that way - push button or jumper - Breaks the circuit