I'm throwing this out as an addition to the knowledge base. I'm certain skilled craftsmen can really improve on my crude attempt. Yes the cover of the FP-29 is the culprit. Remove the cover and the fan noise is WAY down. I tried to see if it could be reduced using various methods and I'm certain some others have gone down those roads as well. The case is a good resonator for that "hum" when the fan is operating. I came close to modifying the fan operation. I tried turning the fan around (blow out instead of in). Tried a completely different fan figuring a change in speed might reduce the noise. What I did find was that if I lifted the case enough to provide about a half inch of clearance below the lower lip of the case, the noise was greatly attenuated. Why not more ventilation? I purchased some hole stock, spec below.
Perforated Sheet, Carbon Steel, Mill Finish, Alloy Type 1008, Cold Rolled Temper, Length 40 inches, Width 36 inches, Thickness 0.029 inches, Gauge 22, Hole Dia. 0.156 inches, Hole Shape Round, Hole Pattern Staggered, Center Spacing 3/16 inches, Open Area 63%, Length Tolerance +/-0.125 inches, Width Tolerance +0.250 inches, Thickness Tolerance +/-0.003 inches, Typical Hardness 95,000, Hardness Scale Brinnell, Tensile Strength 49,000, Yield Strength 42,000
and proceeded to make a replacement cover. My measurements for the replacement was 37.1 CM. by 33 CM. I do not own a shear or a brake so the results were crude by even my standards. I used two wooden pieces and clamps to make the bends. After the bending I was slightly long on one edge so a final trim cut got me there. There is enough forgiveness in front to back and down the sides so measurements are somewhat forgiving. The material I used was not as rigid as the original case cover so it was easier to work, but not as mechanically strong as the original. The mounting holes are interesting. I had 7 of the original 10 screws line up without any drilling. Good enough for me! The supply always ran cool so I really can't comment on any improvement in that area. Totally unscientific results were that I had two FP-29s running at the same time about 5 feet apart. At about 1 1/2 feet from the modified one both sounded about the same level.
Those are the results of today's experiment. 73 John AA3M
UPDATE!!! 7/24/2014 Made second cover. This one fit better than original and ALL 10 screw holes lined up!
UPDATE UPDATE!!! 8/3/2014 I have a very limited number of covers available if someone is interested.
UPDATE UPDATE UPDATE!!! 4/30/2017 Sorry, No longer available......... My contact email is good on QRZ.com
