Installing a DangerDen NV-78 Waterblock on an EVGA 7800GT

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Detailed How-To – Robert Galewaler

I have cooled my CPU for a while now and have achieved a stable and quiet overclocked system.
As I was designing my water cooling system, I did a little overkill on the radiator and fan.
The radiator is from an F-150 and the fan is a 160 mm capable of 235 CFM @ 12V. Also these items were inexpensive too, which is really the reason I have then. The heater core was about $22 and the fan is available for $12 shipped.

The radiator was converted to ½” pipe with a torch. I heated up just the base of the piping and the older pipes just slipped out with the help of pliers. I proceeded to install ½” copper straight pipes to make my life easier. A little bit of soldering or plumbing know how is helpful.

The only issue you can have is heating the pipes too much and melting the solder in the fin area, causing a leak. You can fill the radiator with a bit of water to reduce the temperatures for the fin area; however, be careful as the steam can escape where you are heating the pipes. Use a pair of pliers to gently lift the pipes in the radiator and the solder, when melted enough, will cause the old pipes to slip out.

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The fan was found online; however, I found out about the fan in a forum. The fan is as loud as a jet airliner! Not really, but it’s about 53 dBA when run at 12v – however at 7-9v its very quiet. The smaller fan is a normal 80 mm. Most small 80-120 mm fans can move 20-50 cfm depending on speed. This larger fan can move 80-120 cfm and still be fairly quiet.

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Since I was already water cooling my computer, I thought I would also water cool the video card to keep it cool and quiet. The newer video cards are faster and they are also louder and put out more heat. In order to cool these, you need a faster fan which makes them louder. There is also a size and height restriction to video card coolers, unlike a CPU cooler. Most cards are designed so they can be used in pairs, such as Ati’s Crossfire or Nvidia’s SLI. This restricts the card cooler’s size and height.

Enter the NV-78 cooler:

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This VGA water block is designed to cool the Nvidia’s 7800 GT or GTX with 256 megabytes of RAM; there is also a 512 megabyte version. There is also an SLI version, so you can have 2 coolers installed. The cooler I have is actually half of an SLI cooler. The SLI versions have an outlet on the opposite side of the cooler so the water can pass to the next cooler with a very short tube.

There is an article that shows the memory and GPU can actually influence the way heat flows. If the RAM does not have heat sinks and the GPU is very hot, the memory can get hot as well. Conversely, if the GPU is cool but the memory runs hot, the GPU gets hot also. This is due to the many copper traces between the GPU and memory modules. The NV-78 cooler is unique in that it cools both the memory and the GPU – most VGA blocks only cool the GPU and use RAM sinks for the memory modules.

This is the EVGA 7800GT I purchased a week ago:

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The first thing you need to do is remove the stock heatsink/fan unit.
There are 9 screws holding the heatsink to the card. In the picture below you can see the 5 screws that hold the cooler to the memory have been removed and then there are 4 over the GPU:

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The cooler removed – this was rather easy. Just pull the cooler straight off. Notice the memory thermal pads – they were fairly thick and almost seemed like wet cloth. The pads were easily removed with your fingers.
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This is how the video card looked after removing the cooler and memory heatsink pads:

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The GPU and memory were cleaned with Cotton tipped sticks and alcohol.
All cleaned up and almost ready for the water block:

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I also cleaned up the water block just to be sure there were no finger prints or anything else on the cooler’s copper pads. There were clear plastic shields on the water blocks memory modules – these should be removed.

The four all-threads were screwed into the block using an old trick: First start the rods by hand, then thread two of the brass nuts onto the same thread. Hold the bottom nut tight and tighten the top nut onto the bottom nut. Then turn the top nut clockwise, which will turn the all-thread until the all-thread reaches bottom. Then unscrew both nuts from each other. Turn the top counter clockwise and the bottom clockwise. Remove both and repeat for the other threads.

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The video card got the Arctic Ceramic treatment – a single drop in the center of the GPU and the eight memory modules. The compound does not have to be spread out as the pressure from the blocks will squeeze the compound over the chips and fill the gaps.

The card is now inserted into the four metal all threads:

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A neoprene gasket and a clear polycarbonate piece are inserted over the four posts:

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The four springs, washers, and brass nuts are inserted. To tighten the card evenly, turn the opposite screws 1-2 turns. Then turn the other opposite two nuts the same amount. The nuts are tightened to 60% of spring length. Then the five screws are inserted. Two screws are shorter and are used near the top of the card. Tighten till they seat, then 14/-1/2 turns and no more. In 48 hours, check the card to see if it is still tight.

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Get a good look as you will never see this side again. The reason is the card is designed with the core facing the bottom of the computer in a tower system. If it was a desktop case, you could see this if the window were on the top as in a home theater case.

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Ready to cut the outlet hose. Pump was off of course.
This is the return line from the CPU to the radiator.
The hose was cut and the cooling liquid was drained into a bowl.

The card was installed and the hoses were connected in line with the CPU and radiator. Now all you need to do is hope there are no leaks.
The GPU installed and being leak tested – this should be for 24 hours.

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Well there was a small leak in the outlet line from the GPU cooler. A pair of pliers snugged up the clamp and all’s well.

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Now how does it perform?

The temps are from the on-board diode. At idle, the temp for the GPU was 44ºC with the standard air cooler; with the NV-78 water block, at idle the temp for the GPU is 33ºC

The temperature under load is 41ºC, which is lower than the idle temp with air cooling!

Is this affecting the CPU temperatures?

Prior to the GPU water block installation, the CPU indicated 2 degrees above ambient at idle. The temperature was 22.5ºC. The idle temperature is the same with the GPU block installed. When 3D Mark 2006 was running, the CPU core actually had a 1ºC rise in temps from what they were under load before – 32ºC under load with out GPU and 33ºC with.

I did notice the Motherboard temperature actually decreased by a few degrees, probably due the GPU not dumping hot air into the case. Case or mother board temps were almost always 29-30ºC – now I am getting 28ºC.

In conclusion, GPU temperatures are lower, the motherboard runs slightly cooler, the CPU has not been adversely affected and the noise level has decreased a bit when playing games.

Was the Cooler worth the $125 I paid? For the noise reduction, yes it was.

Robert Galewaler

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