Video card fans (Radeon 9100). What is the voltage? EDIT: Added resistor to fan wire: Now it's quiet! :)

[Eug]

What is the voltage used for fans attached to video cards? I have a Radeon 9100.

The reason I ask is if it's possible to undervolt it using a connection to the PSU instead.

 

[mechBgon]

I think they're usually 5 volts. If you know anyone with a voltmeter, you might borrow it and confirm what voltage you have there.

 

[godmare]

Originally posted by: Eug
What is the voltage used for fans attached to video cards? I have a Radeon 9100.

The fan stock fan on my GF4 is 12 volts, and every aftermarket chipset/vga cooler I've seen is 12 volts.

The reason I ask is if it's possible to undervolt it using a connection to the PSU instead.

I have my 2-pin connector on a 3-pin adapter, running to a 7volted line directly off of my PSU. There was no change in fan speed from my video card header to my 12 volt PSU connector (before I dropped the voltage to 7, that is .)

Insane3D has advocated in your thread on your video card and in at least one other place these. he says it cools his retail 8500 oc'ed to 300/300 with no problem.

 

[RalfHutter]

The fan on my Radeon 8500 runs at 12 volts. My guess is that all factory vidcard fans run at 12v.

 

[Eug]

OK thx people. Good news if it's 12 V. Easily undervoltable.

I guess I'll start at 5 V and see how it works. That way I won't blow up the fan if it just happens to be some odd voltage.

 

[Eug]

Nope. Definitely not 12 V. Put it on 5 V, and it didn't seem much quieter. Stuck it on 12 V and it was friggin' dustbuster.

I guess I'll have to get a great big heatsink.

 

[OulOat]

Or you can use an resistor and lower the voltage some more.

 

[Eug]

Originally posted by: OulOat
Or you can use an resistor and lower the voltage some more.

I suppose, but I would not have any idea which one to buy.

I have zero training in electronics.

Maybe I shouldn't be hacking my wires...

 

[OulOat]

Find out what current your fan needs and use the equation Voltage = Current * Resistance to find out which resistor you should get. For example, say your fan requires .1 Amps of current and you want the resistor to dispel 1 V, you would need a 10 Ohm resistor. Then just insert the resistor in either one of the wires and you would lower the voltage your fan gets by 1 V. Simple mod.

Or if you feel that is too complicated, you can just get a Crystal Orb (the only ThermalTake product I like), lap the nickel off the bottom (3 hours of work), and use it as your fan. It will cool very well at 7 Vs and is pretty quiet.

 

[Eug]

Originally posted by: OulOat
Find out what current your fan needs and use the equation Voltage = Current * Resistance to find out which resistor you should get. For example, say your fan requires .1 Amps of current and you want the resistor to dispel 1 V, you would need a 10 Ohm resistor. Then just insert the resistor in either one of the wires and you would lower the voltage your fan gets by 1 V. Simple mod.

Or if you feel that is too complicated, you can just get a Crystal Orb (the only ThermalTake product I like), lap the nickel off the bottom (3 hours of work), and use it as your fan. It will cool very well at 7 Vs and is pretty quiet.

OK Will look into the resistor. I might have to do trial an error. Grab a 5 Ohm, 20 Ohm, and 10 Ohm. Anything else I need to know?

The new fan is not an option because I have no empty PCI slots. (BX board with 3 ISA slots and only 4 PCI slots.)

 

[OulOat]

Radioshack sells resistors, but by 5, 100, or 500 pack. You might just want to buy a 5 pack of the 5 Ohm resistors and hook as many up in series (one after the other) to get more resistance. When they are in series, the sum of the resistors equal the total resistance, which is what you use in the V=IR equation. You don't have to worry about the power of the resistors since you are just working with a simple fan.

 

[Insane3D]

Eug, as I told you in the other thread, the Radeon 8500/9100 can be run with passive cooling. I have had mine running fanless and overclocked for over 6 months with no problems. The 45mm HS I replaced the stock one with fits perfectly, and leaves plenty of room for your PCI slot below the AGP. Here is a picutre of it in my system to show you how shallow it is..

You can just see the fins to the left of the white stock fan plug

As you can see from that picture, the actual surface mounted caps onthe card are much taller than the HS is.



Edit:

Also, if you felt it was getting too hot, you could just get a standard 45mmx45mmx10mm low RPM ball bearing fan and run it @ 7v.

 

[Naythn]

Are you using a swiftech heatsink to passively cool the northbridge? :Q

 

[Insane3D]

Originally posted by: Naythn
Are you using a swiftech heatsink to passively cool the northbridge? :Q

Yes. See here.

 

[Eug]

Yeah, I was thinking about the resistor thing since that way I can just go to radio shack. The alpha also seems like a good idea but nobody sells it locally. I don't want to wait a 2 weeks for US mail order. Plus although I've done a heatsink mod a couple of times, I'm getting nervous these days. One guy on the radeon forums just ripped his GPU clean off with the heatsink. :Q I dunno if he had epoxied the thing beforehand though.

 

[Eug]

Well, whaddya know. I popped into the local surplus electronics store and there they were. A whole box of surplus ATI video card heatsink fans. 5 V 0.15 A. Anyways I picked up some 8.5 and 22 Ohm resistors for US$0.02 each. 1 W rating for these things. BIG. I'll have to put tuck them away nicely somewhere.

Wish me luck...

 

[Eug]

Pic!

Basically all I did is splice one 22 Ohm resistor into the fan wire. Now my PC is quiet.

I couldn't lower the voltage, since the fan is already at 5V. I also tried adding another 8.5 Ohm resistor for a total of 30.5 Ohms, but the fan wouldn't start.