Odd PSU issue - loud GPU fan

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I purchased a Prime TX-750 and noticed the GPU fan randomly ramps up to 100% during gameplay. It becomes extremely loud under certain occasions. I swapped it for an Asus Thor 850W, and the GPU remains whsiper quiet during gameplay. Tested it with the same game and same scene (Borderlands Pre-Sequel).

Could the TX-750 be faulty? It's not coil whine. I measure the RPM using MSI Afterburner and it always ramps up to 1800rpm+ time from time with the Prime, but doesn't appear to go past 1200 rpm with the Asus.

 

[OZONE]

This is the graphics card fan which spins to infinity. The PSU remains quiet either way.

 

[OZONE]

You haven't clarified anything. Is this a Corsair TX750-M and is it mounted in the bottom of the case with the fan facing up? If you have the psu fan facing up then the gpu fans will be fighting with the psu for airflow and will have to work harder to cool your gpu. In this situation the Asus psu wouldn't cause the gpu fan to work harder as it has a zero rpm mode which the Corsair doesn't have. If the Corsair psu fan is facing the gpu they will both be fighting for airflow hence the gpu fans spinning faster.

It's a Seasonic Prime TX-750.

In both instances I had the fans facing down, and I disabled the zero RPM mode.