Christian Marchand

2230 power supplies have also noisy fan at  turn on unit unloaded.
Bought a new 2231A-30-3 new from tek  for normal use in quiet lab not warfield. 
After 6 x monthes of  daily use on workbench the fan become runing at full speed at power turn on . Noise around 55 dB . UW
Previously the fan was quiet at power turn on and not runiing until supply was loaded during sevral hours of use but never loudly. 
We have a lot of instruments in lab and cannot accept noisy fans in addition....
Tek support required the 2231-30-3 # 802196102757810138 to be back to their support center  at Germering Germany November 2022.
Kept more than  one month in their work shop as they argue unit had no issue but due to waranty time  they replaced it with new one
#80219612777570009.
But alas the new one was correct with no fan runing full speed at turn on during the first eight monthes . But now it as the same issue as
the first supply had . It is still under waranty but  I am not sure they have again enough in stock to replace again .

There is no technical reason for fan to run at full speed at power on specially when power supply is unloaded while basic
principles of calibration allows any electronic instruments to have some warm up for stability.. By the way there is 
no difference when unit is loaded for several hours with no excessive amps and exception to the uncontrolled fan power supply had
always been operationg for voltage and current very functionally and precise 
Of course we could probably replace white aluminium pipe organ like original heatsink with a tuned black anodized one to avoid sound resonancebut fan control must be done by the software and Tek support does not or don't want offer some up-grade .

At least they probably could not offer up-grade to correct this design error and this power supply will be up-graded with Nantua adapted
fan . And I am sure the Tek community has more experience ....