Recently I was monitoring the HF bands listening for a signal from a rather rare country (Crozet Island). Darn noisy fan! Yep, the fan on one of my shack power supplies was irritatingly loud! The power supply is a switching power supply manufactured by MFJ, specifically the MFJ-4245 MV. It can easily deliver 40 Amps, is twin metered for Amps and Volts. Voltage can be set exactly where you want. All in all, it works very well, except for the noisy fans. MFJ does keep their cost down by using a "run of the mill" 4 inch fan. (This supply uses 2 fans). I called HRO in Salem NH, ready to order a new supply. I really like the sales staff there - they don't try to "oversell". They questioned me, knowing the supply was relatively new (pre covid) because they "keep track" of transactions. They suggested I check out "U-Tube" for a video on this problem. For less than $19.00 per fan I ordered new fans as, suggested by the video. Got them from AMAZON. The fan is produced in AUSTRIA. It is the NOCTUA NF-A8 FLX.
Was the effort worth the time and dollars? YOU BET IT WAS! When I turned the supply back on the fans were so quiet I thought I wired something incorrectly. I could not hear them operating. I held a tissue near the fan output and saw it move. Indeed the fans were operational. I am very happy and plan on changing out fans of this type in any equipment including my computer tower. Thank you to the HRO Staff for putting me onto this fix.