[SOLVED] Do three pin dc fans spin at their rated rpm?

[Deleted member 2849646]

Hi,

i’m thinking of buying a 3pin noctua a6-flx to replace a 2pin fan in a PSU. I was just wondering whether there’s any mechanism a psu has to regulate the rpm of the psu fan, or does it run at the rpm the fan is rated for? Wasn’t sure whether to post this here or in the power section. Apologies if it’s in the wrong place.

thanks!

 

[CountMike]

Hi,

i’m thinking of buying a 3pin noctua a6-flx to replace a 2pin fan in a PSU. I was just wondering whether there’s any mechanism a psu has to regulate the rpm of the psu fan, or does it run at the rpm the fan is rated for? Wasn’t sure whether to post this here or in the power section. Apologies if it’s in the wrong place.

thanks!

Depends on PSU in question, most have no fan udjustment at all, some are just binary (on/off), Fully adjustable ones just manipulate voltage according to temperature sensor, In any case using only 2 pins will make it run full speed only.

 

[Mr5oh]

In any case using only 2 pins will make it run full speed only.

A 2 pin setup could (in theory) still use voltage to vary RPM?

 

[CountMike]

A 2 pin setup could (in theory) still use voltage to vary RPM?

Yes, third pin is just RPM counter.
Btw. Voltage change doesn't regulate speed directly in that kind of motor but regulates it's power, With lower voltage motor doesn't have as much power so air resistance makes it turn slower.

 

[geofelt]

What is your objective for replacing the psu fan?

I would not be going about messing with the internals of a psu.
Buy a replacement psu if you need to.

 

[Deleted member 2849646]

A 2 pin setup could (in theory) still use voltage to vary RPM?

That's what I thought? Would have thought some clever psu's would have that kind of built in feature?

 

[geofelt]

Power supplies are able to control fan speeds.
With a 2 pin fan, that will be done by voltage control.
Expect such controls to be proprietary.

 

[DSzymborski]

This is an awful lot of work and cost to replace the fan on a ancient OEM PSU in a prebuilt, assuming this is the same PSU you ask in the other threads on this subject.

Just replace the PSU. From the bit of PCB you showed us in one of those other threads, this isn't exactly some diamond in the rough Delta-made OEM PSU.

 

[Deleted member 2849646]

Power supplies are able to control fan speeds.
With a 2 pin fan, that will be done by voltage control.
Expect such controls to be proprietary.

If i'm just soldering on black to black and red to red, it should still work (fan speed control) if used on the non original fan right? Or does the psu have a way to detect that a different fan is being used and hence not allowing it to work?

Oh and to answer your other question, it's to get rid of the annoying rattle, PSU is apparently proprietary and a like of like crappy one costs £40 vs fan which costs £14. Just works out cheaper and better replacing the fan rather than replacing the psu with another crappy psu.

 

[DSzymborski]

If i'm just soldering on black to black and red to red, it should still work (fan speed control) if used on the non original fan right? Or does the psu have a way to detect that a different fan is being used and hence not allowing it to work?

Oh and to answer your other question, it's to get rid of the annoying rattle, PSU is apparently proprietary and a like of like crappy one costs £40 vs fan which costs £14. Just works out cheaper and better replacing the fan rather than replacing the psu with another crappy psu.

If you gave us more details about the PC and the PSU, we might have other ideas for you. If this is a PSU that's like a decade old, a new crappy PSU may still be a better investment than a fan on an ancient crappy PSU.

 

[Deleted member 2849646]

This is an awful lot of work and cost to replace the fan on a ancient OEM PSU in a prebuilt, assuming this is the same PSU you ask in the other threads on this subject.

Just replace the PSU. From the bit of PCB you showed us in one of those other threads, this isn't exactly some diamond in the rough Delta-made OEM PSU.

What would I replace the PSU with though? It's not like I have any option other than get a like-for-like replacement (proprietary dell psu), the cost of which would be triple the cost of a fan, and the fan would still be a crappy stock fan.

 

[DSzymborski]

What would I replace the PSU with though? It's not like I have any option other than get a like-for-like replacement (proprietary dell psu), the cost of which would be triple the cost of a fan, and the fan would still be a crappy stock fan.

Well, if we had information, we might have ideas.