Leadtek 6800GT/Ultra/NU silent mod

They make noise, too.

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Leadtek 6800GT/Ultra/NU silent mod

Post by myshkin » Thu Jun 02, 2005 10:16 am

I've created an interesting mod to silence leadtek 6800 based graphics cards. They come with a custom copper cooler, which is called air-surround, that uses a 50mm fan. It's quieter than the standard 6800 cooler, but still loud if you care about silent computing. The main thing is it being rather large and solid copper, it's got excellent possibilities.


with this cooler at stock, my 6800GT (@ultra speeds) runs about 60c idle, and 85c load. The cpuburn equivalent for loading your graphics card is generally agreed to be rthdribl - http://www.daionet.gr.jp/~masa/rthdribl/#Download.

Now for the mod. Firstly i junked the horribly restrictive air filter over the fan. This improved things a little, then i disconnected the fan and put a 60mm fan over the air filter hole at 7v, this was much quieter, but not even close to perceptibly silent.

In the photo you can see there's a plastic shroud, intended to guide the fan's air flow over the copper cooler beneath it. To remove the shroud, you have to remove the heatsink, as it's screwed on from the underneath of the heatsink. I thought removing the shroud would be wise as it limits the amount of air you can get to the heatsink under it, you can't go bigger than 60mm.

While i was doing that, i took a look at the thermal compound on the gpu, it appears to be silver based, but i cleaned it off and put some fresh AS5 on there, about a rice grain sized blob, as the NV40 uses a heatspreader.

With the shroud gone, the fan options are a lot better, with some experimenting i found frameless fans worked quiter and cooler, it's a wide heatsink so the frameless fans get more air across the heatsink.

The upper size limit for a fan is 92mm, due to the width of the card itself. Unfortunately the only 92mm fan i have to hand at the moment has a dodgy bearing and is clicky. however i still tested with the 92mm fan, as well as an 80mm.

it seems 5v to the fan is enough for cooling the card. The actual results were:

80mm frameless fan @ 5v - idle 55c, load 79c.
92mm frameless fan @ 5v - idle 53c, load 74c.

That's with a closed pc case too, after leaving rthdribl for half an hour. I did briefly test with 7v on the fans, but fan whir became perceptible, and turbulent noise also appeared, probably due to the many fins on the heatsink. At 7v you can decrease temps by about 2-3c.

For now i'm running with the 80mm fan on it, frameless, and only 5v, and it is completely silent. Temperature is also down from stock cooling by about 5-6c. It's win-win. :)

I don't have a proper digital camera, this is taken on my SE mobile phone and so a bit blurry, however it gives an idea of the setup and the differences from the stock cooling.


I'm really pleased with this mod, it's quite amazing to have such a powerful card run silently and relatively cool with such little effort. :D

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Post by @TOMMY@ » Thu Jun 02, 2005 5:06 pm

Very nice mod

you need a digicam :P

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Leadtek 6800LE also

Post by freefall » Sat Jun 04, 2005 9:07 am

Marvelous !

That aggressive little 55mm default fan was nasty.

How did you attach your fan? I'm thinking some parts of the shroud are reusable. If you cut off the four black feet (pins) and re-screw them back on, maybe you can build some sort of platform.

I glued on a framed 12V 80mm fan and it's already sounding better. Temp is a bit down, I think. Seems to peek at 70 C under gaming, stable at 61 C. And my 6800 LE is both unlocked and overclocked, and has core voltage upped with 0.1V. I've only one exhaust, in the PSU.

Now I need a silent 80 mm.. I can get 5 of these for $18 total:
Everflow 80 mm, 15 dBA, 1500 RPM, 23.7 CFM, 12 V.

Think one of those would suffice on the gfx card at 5V?

cheers :D

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Post by myshkin » Sat Jun 04, 2005 9:52 am

Hi, i attached the fan using the four arms that linked the fan hub to the frame i cut off. You have four arms, one of which holds the wiring out of the fan blades, so i put a dab of good old superglue on the bottom tip each of the other 3 arms, and aligned the fan arms so the wires come out the bottom if you look at the second pic in my post. The three arms with glue on each just about reach the 3 raises sections of the heatsink at the top and on both sides.

I bought a new 92mm fan yesterday, replacing the 80mm, but it attaches in an identical fashion. :)

It's a 2500rpm case fan with the frame cut off, so at 5v it does about 800-900rpm. That gives an idle of about 53c, and a load of about 75c.

I've never used an everflow fan, but i can bet that if it does 1500rpm at 12v, running it at 5v will not produce enough CFM to cool the card properly. You could try it at 7v though. You need a noticeable amount of air pushed over these cards for them to cool properly.

About reusing the shroud pins as a platform, you could try, although the spacing for them won't fit any fan frames anyhow. I'm keeping mine in one piece, along with the original fan, should i ever need to claim on the warranty i can refit everything to stock. ;)

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Post by uzibear » Thu Sep 29, 2005 1:10 pm

i removed the shroud, replaced the thermal paste with AS5. now i have a 92mm and 80mm fan. i think i'll use the 80mm as the 92mm has too large an area in the middle that restricts air. anyway, i'm wondering what sort of glue to use to attatch the fan to the heatsink. looks like it will fit nicely with two edges of the case of the fan resting on the "solid" part f inner edge of teh heatsink. will crazy glue or super glue hold up even when it gets really hot?

also: how do you undervolt to 5v? my 80mm fan has a red, black and yellow wire. the connector to the the card has a red and black wire. i assume the yellow wire from the 80mm fan is the monitoring wire. are you guys running the fan directly off your psu rather than using the connector on the card? i have a zalman fanmate at my disposal as well so that's another possibility. suggestions?

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Post by fanerman91 » Sat Dec 30, 2006 3:46 pm

Thanks for this thread.

Due to random circumstances, I managed to get a hold of a Leadtek 6800 Ultra and so I had a slight upgrade from my BFG 6800 NU. I was thinking of buying an aftermarket heatsink, but I found this thread. I ended up taking my Leadtek apart and I stuck a 92mm fan onto the heatsink. I actually tied it in place with a piece of string, but I'm getting better temps than I used to.

Thanks for the heads up. Nice to take advantage of that quality heatsink that's already in place.

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