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 Post subject: mounting 120mm pwm fan directly to 4890 PWM fan header
PostPosted: Wed Jun 24, 2009 9:22 pm 
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Joined: Sat Mar 08, 2008 1:37 pm
Posts: 4
Location: Denmark
i got my fingers in some very cheap 120mm pwm fans, and wanted to experiment a little.

i cut of the original fan plug and soldered a pwm fan plug from another (dead) graphics card. So now instead of plugging the 120mm fan to the mobo it plugs nicely into the 4890 card.

i thought this would would be a great way to get some automatically and programmable fan control for the vga cooler (accelero S1 rev 2)
however the fan keep spinning af maximum speed (1000rpm) no matter what the fan speed is adjusted to.
I've used GPU-z to verify that the PWM signal actuarial goes up and down, and it does. the fan just keep spinning at 1000rpm.


is there some kind of difference in the pwm signal between the vga cooler and a normal case fan, or any other reason this should work?
what can i do to make this work ?


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 Post subject:
PostPosted: Thu Jun 25, 2009 12:36 am 
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Joined: Sun Nov 09, 2003 7:18 am
Posts: 1121
Location: UK
Hi, I can think of two possibilities.
- CPU / case PWM fans work differently to those on graphics cards.
- Your wiring is wrong. I guess you have the +ve / -ve correct or the fan wouldn't run at all. Maybe you have the PWM and RPM monitor the wrong way round? I believe a PWM fan will run 100% if it receives no PWM signal.
Other than that I don't know.
Good luck, Seb

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 Post subject:
PostPosted: Thu Jun 25, 2009 1:50 am 
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Location: UK
If there is a motherboard PWM fan (4 pin) header you could alternatively run all the PWM fans off that using for example the Akasa PWM splitter - smart fan cable (AK-CB002). This has the advantage as well of drawing power from the PSU via a molex connector and not through the motherboard.


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 Post subject:
PostPosted: Sat Jun 27, 2009 5:01 am 
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Joined: Sat Mar 08, 2008 1:37 pm
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Location: Denmark
@Sebrad
i have been giving thought on the wiring. but since the fan i spinning and i can measure the RPM its seems not to be the case

however i did not verify that PWM did work on the fan before using it. so maye jsut faulty fan. lucky i got several of these.
i have teste another on and the pwm on the mobo works fine.


@Lodestar
this wil lbe my backup solutions howeer i wish to avoid that.
if i mount the fan onto the mobo i have no automatically way of increasing the speed according to gpu temp. as speedfan does not read my gpu temp.
Neither on my 4870 or my 4890 did speedfan read the gpu temp.
however it works perfectly if i put in a gtx260.


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 Post subject:
PostPosted: Thu Jul 02, 2009 1:46 pm 
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Joined: Sat Mar 08, 2008 1:37 pm
Posts: 4
Location: Denmark
i did some more testing to day.
i threw out the first fan. after i desoldered the fanheader.

i also found a 4 pin pwm fan female plug. So now i have made an adapter , so that you can plug a normal pwm fan into af graphics card pwm.

testec with a new fan and guexs what. .. exactlyt 1003rpm again.

now this time i did test the fan and it did ran 1500 at full sped on my mobo. i also could adjust it up and and down. i even triede settignsnhe fan control modeto pwm in the gigabyte bios and is seems to be pwm controlled.


how ever, attached to the 4890 no matter what i set the fanspeed to. it simple doesn't change the rpm on the fan.-

maybe my gfxcard does not support pwm afterall :-( lucky le i got my other 4890 (exact same model) so i can test with the normal 4890 fan.


i damn hope that i can get this adapter to work so that i can get them factory made


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 Post subject:
PostPosted: Mon Jul 20, 2009 12:17 pm 
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Joined: Sat Mar 08, 2008 1:37 pm
Posts: 4
Location: Denmark
i finally found out that the problem lies in the cheap pwm fan they simply doesn't work like normal.

if you attach the fan to voltage only the fan rotast at 1000rpm and by reducing voltage control you can adjust the speed down .
if you attach them to PWM controlled header they minimum speeds is 1000 and maximum speeds is 1500. so the fan does however speed up with the pwm kontrol rather then speed down.

never seen another pwm fan act like that.


i attached an artic coolings pwm fan and it works flawless.
They should consider making these adapters and put nto the accelero S1.
its so nice to have the machine runs without the fan while surfing the web and then automatically spin up to 800rpm when gaming.


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