Supermicro PWS-721P-R1 PSU Fan speed control

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Morpheus187

New Member
May 8, 2017
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Hi There

I've got issues with the super micro power supply noise level ( PWS-721P-1R )

It's not that noisy but I contacted supermicro and they sent me a specification sheet with informations regarding a pin 17 connector which can change the fan into quite mode
I'm however not really able to understand what I need to do, there is no jumper to set, I have no idea how I get a TTL low signal on that pin.



I also checked the power distribution board but havn't found anything I would try to mess with.

I've attached the coresponding pages from the spec manual.

P1.png p2.png

Maybe some of you guys have any idea how I can proceed

Thank you

Morpheus
 

pricklypunter

Well-Known Member
Nov 10, 2015
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It simply means, to place the Fan in "Quiet" mode, you need to ground pin 17 on the 20 pin connector :)
Leaving pin 17 high or not connected (floating) enables normal PWM mode.
 

Morpheus187

New Member
May 8, 2017
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I've now unplugged pin 20 from the ATX connector ( the white cable which was intended for -5V ) But when I put it to ground I don't notice any difference in fan speed. I guess the PSU is already running in "quite" mode with 8700 RPM. I think I would only see a difference when I put on a high load, maybe the fan would only spin up to 10'000 RPM instead of 15k or so.

But thanks for the explanation. After reading the manual over and over again it became also clear to me what cable and pin they meant.
 

bwfan

New Member
Feb 10, 2018
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It simply means, to place the Fan in "Quiet" mode, you need to ground pin 17 on the 20 pin connector :)
Leaving pin 17 high or not connected (floating) enables normal PWM mode.
Good evening,

Can you elaborate on this? Is this the ATX 20 pin connector or the pins on the PSU board itself.

Thanks

Sent from my SM-G950W using Tapatalk
 

pricklypunter

Well-Known Member
Nov 10, 2015
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Ground pin 17 on the 20 pin ATX connector to place it in quiet mode. Obviously you could ground it at either end of the cable form to achieve the same goal :)
 
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Dennip

New Member
Jun 26, 2018
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Sorry to bump an old thread guys but I just successfully did this!

I went in circles for a while trying to figure out what pin 17 was exactly and even cracked open the PSU, given that Morpheus187, sadi it didnt work for him, but in the end its as simple as you guys say:

The white cable on the ATX Motherboard connector, which used to be -5v, is now used as 'Pin 17', the quiet mode connector.

Simply connect this white cable to any of the black (ground) cables on the same ATX mobo header and your PSU will be in quiet mode (and very quiet at that!)

I have the pws-1k21p-1r and don;t draw anything close to 1200 watts so i'm not too worried about them getting too hot or anything. Besides the fans still ramp up and down when they want to, but nowhere near max speed and when the machine is on and idling they're practically silent.

Some pics of my temporary setup with test probes:
Imgur
 

Breit

New Member
Apr 13, 2019
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Sorry for resurrecting this, but I tested this on a Supermicro CSE-747TQ chassis to no avail. Maybe there is something I overlooked? Or does this only work on the PWS-1K21P-1R and the PWS-721P-1R?
I've got two sets of redundant PSUs for this chassis available, but neither of these PSUs responded or changed behaviour when pulling pin #17 to ground. The PSUs are dual PWS-1K62p-1R (1620W 80+ Platinum) and dual PWS-1K41P-1R (1400W 80+ Gold) respectively.
Both PSUs have their fans spinning while in standby (system switched off), which is very annoying. I had hoped to silence these PSUs at least when in standby.