hi all,
i've recently bought a secondhand hx620 psu which i thought to be a perfect silent one. However, it seems pretty noisy - as if you could hear som ticking-clicking several times a second. So i'm thinking to replace the fan.
Could somebody recommend a silent 120mm fan that can be used in a psu please? Or if this is a common problem, would you have any other suggestion how to solve it? Thanx in advance

I'ts pretty easy to replace the fan. I did it a couple of years ago on my HX520. Something like a Scythe Kama Flow 2 1400rpm should work well.

I guess every fan that is available and quiet enough for your taste. The general word of caution is to use ball bearing fans since these can handle the horisontal position and endure much higher temperatures. But sleeve fans are made very differently, and whether they can endure the forementioned things dpened much on the anatomy of the specific fan.

If you want BB fan, i would go with GT, they come in wide variery of ranges, here is couple,

Scythe Gentle Typhoon 120mm x 25mm Fan - 1150 RPM (D1225C12B3AP-13)
Scythe Gentle Typhoon 120mm x 25mm Fan - 1450 RPM (D1225C12B4AP-14)

so it won't be as difficult as i thougth should i also consider the rpm? If i put in the 1150 rpm fan, which with it's advertised16dBA seems pretty quiet,could't it be insufficient at some point? Thanx

That all comes down to math. If your system consumes 50-200W depending on work load and components, and your power supply has an efficiency at roughly 80 %, and the resting 20 % is lost in heat, then you will need to dissipate between 10 and 40 W heat. That doesn't require many rpm's for a 120 mm fan, though PSU's are of course more vulnerable to high temperatures than a CPU or a GPU. But nevertheless, not that much airflow is needed. Personally I run a Corsair CX400W with a Scythe Slipstream probably running at 300-400 rpm. The exhaust heat from the fan is very cool, practically ambient temperature, though I haven't check during gaming.

So you can easily run the fan quieter than the 1150 rpm.

Well really depends on the PSU, some will not run them at 12V fully until they are at certain load. I would try to get as close speced as possible as the original fan, just a better quality fan. There might be issues, like some fans have certain starting voltages, and if the PSU is set to feed the fan below what the fan you replace is rated to start with... then it wont work, this is very hard to know, as until you test it you wont know, or if someone like CA_Steve that changed on a HX520 can tell you (thats if he saw what specs were the fan or if the HX520 had certain start voltage, etc). Now GT have can be ran very low, i have 5x GT 1850rpm, and with Scythe Fan controller i can drop them to around 500rpm, but im not sure their start up voltage nor whats the voltage that the HX650 will send to the fan. My guess is that 1150 GT will be fine, but again until you try there is no way to be sure, CA Steve is probably the one that can help you the most here out of the similarity with your PSU.

Ah - forgot about the Gentle Typhoons: lower dB at similar cfm/rpm to the Kama Flow 2's.

SPCR's review shows Corsair's ADDA fan voltage profile on this page. Fan voltage starts at 3.84V. The stock fan is 2200rpm at 12V. Scythe lists the GT's starting voltages here. So, you'd want to get the 1450 or 1850rpm fans with their 3.5V start up voltage.

I didn't find a Scythe listing for the Kama Flow 2's start up voltage. But, X-Bit Labs says it's 2.5V for the 1900rpm and 3V for the 1400rpm.

I don't remember the rpm I put in - too long ago and didn't put it in my sig Somewhere in the 1600-2000rpm range for the original Kama Flow with FDB from Sony. It's inaudible to me.

Really good info from CA_Steve, out of what he find out, i would probably go with the Scythe Gentle Typhoon 120mm x 25mm Fan - 1450 RPM (D1225C12B4AP-14), since it can apparently start at 3.5V, and it has real ball bearing, and its very good fan in my experience in terms of cfms. The 1850RPM should be an option also, since has the same starting voltage of 3.5V, but this fans is much harder to get, and most of the time resellers jack the price because of its demand (to get my 5x GT 1850rpm i waited like 4 months), so seems easier to get 1450 and should be slightly quieter.