Hello,

About 4,5 years ago I bought a P183 case with a CP850 PSU, filled with a bunch of 120mm fans that are all pretty quiet at idle (mix of Scythe and Noctua). In the past year or so I've been noticing increased noise while idle (during gaming it doesn't stand out any more). I've traced the noise to the PSU fan, which sounds worn. It makes a pulsating, almost clicking, noise, and also a whirring noise when you hold your ear next to the case. Seems it's time to replace the fan.

Some links with info on the current fan:
http://www.silentpcreview.com/article971-page3.html
http://www.jonnyguru.com/modules.php?na ... 3&reid=142

Apparently it's a Protechnic / Magic 120x25mm 0.52A fan that's rated for 12VDC, 93CFM, 2800 RPM, at 42 dBA.

Since it's a PWM fan (4 pin header) can I just plonk any other PWM fan in there, even though most are built for much lower RPMs than the 2800 RPMs of the current fan? Won't that confuse the fan controller in the PSU if it expects a certain RPM?

Any recommendations or doesn't it matter that much as long as I get something half-decent?

Thanks in advance for any help you can give me, I'm not afraid to bust that bad boy open but I haven't done this often enough to really know what'll work or not.

Providing you were satisfied by the original fan behaviour, what about picking the very same fan?
Otherwise pick one with a similar (equal or slightly lower) starting voltage.

No, I wasn't that satisfied with the original fan. I stripped all the Antec fans out of the case when I bought it and replaced them with Scythe fans which were much quieter. The PSU was vastly overpowered for the hardware I bought, which meant the fan wasn't really a problem (it never had to work very hard), also because it was deep within the case, but a 42 dbA fan is not something I want to put in again. And I want my next fan to last a bit longer.

Starting voltage is a non-issue for PWM fans, right? I thought they were always on full voltage but with different pulse widths. Although that might be what you meant, not sure how I can get that info though.

I would have thought that any PWM fan with a top speed of 2000+ rpm would be suitable. Possibly the Scythe Grand Flex SM1225GF12SH-P 120mm PWM. This fan has a nominal 600 to 2400 rpm range. It does have an FDB bearing which might make it more suitable for a PSU than the sleeve bearing fans.

That... looks like a really good recommendation, thanks. SPCR isn't too positive about them but there doesn't seem to be much that can go toe-to-toe with the 2400rpm PWM model.

I like loadstar recommendations, the range of operation seems like a good bet for matching the old fan, this grandflex like most Scythe wont stop even under 0% pwm so you the PSU should be able to spin it. This is probably the fan i would chose if i were in your spot.

Some other alternatives,

Scythe Gentle Typhoon 120 mm by Nidec Servo Corp. - 1000-3000 PWM Fan - Sleeved
Higher maximum than the included, and seems to only drop to 1000rpm, but Scythe GT are known for very good statitic preassure, im guessing this higher end versions will be more than enough to cool your psu, have my doubts into 1k rpms minimum into how quiet that would be, but an option if you do require more cooling than what the grandflex can give.

Noiseblocker NB-Multiframe M12-P 120mmx25mm Ultra Silent PWM Fan-1000-2000 RPM - Sleeved
If you were to be fine with 2k rpm max and 1k rpm minium... this could be an option. SPCR did like the M12 in their review, its a matter if the rpms are good enough for you.

That Gentle Typhoon is weird. Everything I can find about it suggests it's not PWM out of the box, but it can be modded to be PWM. So no idea if that shop is selling a modded one or if their info is incorrect. Either way, it has a lower airflow than the Grand Flex, even at a higher RPM.

The Noiseblocker looks like a nice alternative too. It doesn't seem to perform substantially better than the Grand Flex at similar RPMs though.

The Grand Flex comes closer to the specs of the stock fan (wrt RPM and airflow), so I think I'll try it first and see how that works out. I expect it to run at minimum RPM most of the time anyway, so the low starting speed is a big plus over the other alternatives.

Thanks for your additions!

A PM alerted me that I never updated this topic. I did end up going with the aforementioned Scythe Grand Flex SM1225GF12SH-P 120mm PWM fan, and I can report it is a complete success. As hoped the fan never spins up enough to make any discernible noise, so it's even quieter than the original fan was even before it started making clicking noises.

However, installation is not as easy as I hoped! Disassembling the PSU and replacing the fan isn't very hard, but connecting the fan is. The pin-out of the original fan is different from the Scythe. IIRC you have to basically swap the pins from left to right, but as it was a while ago I'm not 100% sure. Take a good look at the pin-out of the original fan and you should be able to figure it out, once I got over my hesitation to mess with the pin-out it worked on the first try.

Other than that I have nothing but good things to say about this mod and I'm really happy I did it. My wife's computer has the same PSU and I'll probably end up doing that one too at some point.

I am pleased to report that I was also able to successfully replace the (failing) stock fan on my CP850 with a Scythe Grand Flex. I did have to reverse the fan pinout as Vinz mentioned.

Ok Im exactly in the same situation as the OP was.
I would like to replace the original fan to the recommended Scythe one.
As the OP wrote in order to be able to do that you need to swap the fan pinout as its reverse wired.
How do you do this exactly ? Do you reverse the four wires in the Scythe fans female connector ? I dont see how I do that without breaking that plastic piece. Or is there some other method like a buying a reverse wired extension cable ? I didnt found any.

Thanks for any insight !