This is for owners of CM iGreen series. Your mileage might varies with other brand.
Also make sure you switch the mains off and disconnect power before attempting to open the PSU.
Do not attempt to touch the PSU circuit board/bare wiring if you haven't discharged the PSU capacitors. It can be fatal.

Today, I just replaced the stock CM fan with an NMB in my CM iGreen 500W PSU and the difference was just astonishing.
After opening the PSU and looking at the fan, I noticed that the stock fan's sticker was actually bulging. Peeled the sticker and you could see traces of lubricant (which had leaked out). Bad fan. This confirms why it was so loud.

Details :
Bad stock fan- Coolermaster A12025-25BB-2AN-P1 (it's actually a Chinese oem CHB120112DB-O .. no idea who's the real manufacturer) /120mm x 25mm / 12V 0.47A / 93cfm 2600rpm 47dbA

Replacement fan - NMB 4710NL-04W-B50 (older N-series .. only one I could find under short notice) /120mm x 25mm / 12V 0.74A / 92 cfm ? rpm 40dB

N.B You'll need to ensure the replacement fan has 2-pins connector. Failing that, buy some from Pasar Road if you're in KL.
You won't be able to fit a 120mm x 38mm fan into the PSU chassis. It's made for 120mm x 25 mm fan.

Extra work done :
1) remove fan grille permanently
2) isolate fan from PSU chassis using bicycle tube rubber. You can get this from any bicyle shops, just ask for the ones they are throwing away. Use Dunlop contact glue to create 2 rubber layer and cut the sheet to roughly a 10 cent coin size. You will need 8. Before mounting, it's easier if you can pre-drill the holes or if you don't have any drill cut it cross shape. Mount them on both sides to isolate the fan & screw head from the PSU chassis.

Conclusion:
No more noticeable grating noise @ idle and extreme grating noise @ high load. My Centurion 534 Casing is now super quiet at idle, almost makes you wonder if the PC is working.
There is a noticeable noise at high load but it's so low that you can ignore it easily. I wanted to get a quieter fan that could push out ~70-75cfm originally, but the result I got with the NMB high speed (xx-xx-B50 or above) was a pleasant surprise. So I'll stick with it until it gets broken.

Next stop, fully dampen casing with Superlon.

P.S Sorry no pics. Wanted to take some, but too late. I'm not about to dismantle the system again.

This post has been edited by stormcloud: Nov 17 2007, 08:13 PM