Hi, I have an OCZ zt 750w PSU and the 140mm fan isn't very good. Are there any good quiet 140mm fans? or failing that has anyone used a 140 to 120mm converter and mounted the 120mm fan on the outside of the PSU case?

For a PSU you normally need a fan with a low starting voltage, around 3.5 to 4V. A possible candidate is the Nanoxia DX14 1200 rpm model available from UK sources such as this one http://www.watercoolinguk.co.uk/p/Nanoxia-DX-Series-DX14--1200rpm-140x140x25mm_17880.html. There is a review of this fan here http://www.xbitlabs.com/articles/coolers/display/140mm-fan-roundup_4.html.

be quiet! Silent Wings.
Hard to find a good review, mostly forum posts. This fan is used in beQuiet PSUs, too.

I am also looking for the quietest 140 mm fan according to those testing them at silent pc review.

I use slow speed fans. Currently using Scythe 500 rpm 140's in a couple of ways.

Are there any larger?

Nanoxia, EBMPbst and a few others are names I've read just recently. But some are European and I am in USA.

For comparison price, I bought at Platinum PC. They have the Scythe Kazemaru 140 mm 500 rpm with free shipping for $14.00.

What other products can you recommend in that range? Or less? I use an extreme bare bones sort of setup.

Also, in reading around, it was good to hear that silentpcreview is the trusted place for this sort of info.

That is a good fan. It is a quiet fan. And it is an inexpensive fan. The stated average hours of life though are not confidence inspiring.

Agreed, but it is also one of those '140mm' fans which is actually an oversized rotor in a frame with 120mm size mounting holes. So it needs the space of a 140mm fan but won't fit 140mm standard mountings.

the xbitlabs article is a good one. I gotta decide whether i want to invalidate the warranty though, PSUs are the flakiest of parts in my experience (3 died in 6 years).

According to reviews such as this one http://www.hardwareheaven.com/reviews/1291/pg1/ocz-zt-series-750w-power-supply-review-introduction.html this PSU should be reasonably quiet. However, the 140mm fan fitted is rated as 2800 rpm max, so there is the potential for noise under load I would have thought. That said, if the unit is still under warranty you might be better off to RMA it than attempt a fan replacement.

am thinking mine doesnt change with load, just stays on maximum speed.

In my application which is a tweak on CPU cooling i've tried several fans.

The Scythe on an older Sempron moves enough air with the unit on 24.7. But on a new install with an AMD II x3 and using the same 500 rpm fan I'm getting hot readings.

Switching to an older higher rpm fan (the more usual kind found in an older case setup) there is a secondary hum that sounds like flourescent lights. I have to turn the thing off to keep my sanity.

So here is a question for the experts:

At what rpm do those horrible fan hums start?

I'd gladly get a fresh Scythe of a higher rpm if I knew it would stay quiet.

PSU fan speed is normally controlled thermally so that when the system is at idle it might be running at something like 20%/25% of max rpm. The fan should speed up as the power supply gets hotter, either through load and/or a rise in intake air temperature. If it is running flat out all the time then the thermal control has failed, and a warranty replacement should be sought.

The question was about secondary hum on fans.

I have no doubt that the fans are running same speed all the time.

Consistent speed means consistent silence on the current setup. I need to know how much rpm will stay under the speed at which secondary hum is audible.

SEE: 140mm Fans
viewtopic.php?p=546350#p546350

ALSO: Combined PWM and Voltage Controllers for Non-PWM fans
viewtopic.php?p=546412#p546412

Ok. I took a quick look. My Scythe fans work fine in all instances but the quickie review said his wouldn't go.

Platinum PC has the Noctua brand as well with free shipping and I think I should move them up for places a regularly consult for parts.

But last night I figured I had to do something and get a product I know so I got a Scythe 800 rpm which is just above their minimum which I am using now.