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G5 9800 Pro Cooler ReplacementReturn to News Page
Page 2: Arctic Cooling VGA Silencer install on 9800 Pro/G5
(Continued from page 1.)
By John Bartleson
Posted: 10/5/2004

Here on the front of the card is the GPU that does all that fast drawing. Clean the residual thermal compound off both the GPU and the old heatsink. Make sure you get it all off so it won't interfere with heat transfer through the new thermal compound. Arctic recommends removing the compound using tissue and your fingernail. (Avoid touching the GPU contact patch with your finger as you transfer oils from your skin that interfere with the efficient transfer of heat after applying new thermal compound.) Other manufacturers recommend using alcohol. Neither method worked for me. I ended up using acetone, which gave the shiny finish shown here. I can't suggest you use acetone though. It's highly flammable and a health hazard. If you're experienced with acetone and choose to use it, do so in a well-ventilated area with no ignition sources. Don't breathe the fumes or let it touch your skin.
(Acetone was the only thing that worked properly to remove the original thermal cement on my OEM 9800's GPU, mentioned in my Verax G03 install guide also last December. Acetone produced the mirror finish shown in that article's photos. I also included a warning about acetone precautions/hazards but many of us still use it because it cleans very well, dries almost instantly and leaves literally no residue.)

The Big Clamp:
Here's the Silencer assembled to the card. It's super-sized to silently cool the GPU to lower temperatures than other coolers and fans. Arctic claims 47.1°C (117°F) on the high-speed setting. Unfortunately it's so thick it blocks use of the the adjacent PCI slot. It's heavy, too. We'll talk about its weight later.

Here's the reverse side of the card/cooler assembly. The unfortunate gotcha: the big blue clamp won't let the assembly fit in a PowerMac G5 because there's only about 1/4" between the AGP card and the aluminum plate at the bottom of the card compartment. We're going to have to surgically downsize that clamp.

This end view shows how big the clamp really is.

Here's the clamp assembly as it comes from Arctic. The two screws go through the existing holes in the card and screw into the Silencer's heatsink. There's one screw on the upper-left side of the GPU and another on the lower right. Note the button at the center of the plastic housing.

The clamp assembly with its metal beam separated from the plastic housing. In a standard installation, the screws are tightened into the Silencer's heatsink on the other side, the rubber washers are slightly compressed and the beam presses the plastic housing's button against the back of the card at the center of the GPU. This design ensures that the clamping force will be at the center of the GPU even if the screws are unevenly tightened, keeping the heatsink flat on the GPU and ensuring good thermal contact. If the user over-tightens the screws, the beam will bend and no damage will be done. This is a clever design that our clamp mod will retain. Note that the button is the part of the plastic housing that does all the work.

Modding the Clamp:
We can downsize the clamp and retain its original function by turning the beam over so the flanges are on the card side of the beam, then cutting the button out of the blue plastic housing and putting it inside the beam. I used a Dremel tool with a cutoff disk to cut out the button. A hot-knife or hacksaw could also be used. Don't cut too much of the button away - it needs to be wide enough to fit snugly between the beam's flanges.

After the surgery. Arctic employees may want to avert their eyes.

If necessary, use a block sander to adjust the button's width to fit snugly between the flanges.

Push the button into the beam. Make sure that it's centered between the screws.

Trial Fit:
Lay the Silencer down with the screw holes facing up. Turn the card GPU-side down and lay it on the Silencer, lining up the two screw holes. Put the clamp assembly (with all four washers on the screws) in place and thread in the screws. Tighten the screws alternately as much as you can without the beam touching any components on the card. After you install the card in the G5, the two screwheads may touch the bottom of the card compartment, so the beam will be grounded and must not touch any component on the card. I had to bend part of one flange out to clear a component. You could also grind the flanges a little - if the grinding is near the ends of the beam it will not be significantly weakened.

The screw heads will be the highest point on the back of the card and we need as much clearance as we can get, so tighten them as far as possible without the beam touching a component. The beam will be slightly bent. Make sure that the plastic button is centered at the back of the GPU. Important: verify that the Silencer's aluminum block is clamped tightly to the GPU, with no movement or spaces. If you don't have good contact between the GPU and the block, the GPU could overheat and be destroyed in a matter of seconds.The block doesn't completely cover the outline of the GPU. This is OK, the important contact is with the raised inner square of the GPU.

Final Assembly:
Disassemble the Silencer from the card. Plug the Silencer's power cable into the card. Make sure that the old fan is laying in an area of the card that won't interfere with the Silencer's heatsink.

We need to spread a thin layer of thermal compound on the raised inner square of the GPU. The Silencer comes with a tube of silicone compound, but I took no chances and used Arctic Silver 5. Arctic's site at www.arcticsilver.com has very detailed instructions on how to apply the compound. Go there if you're a perfectionist.

Clean the inner square of the GPU again. Also clean the mating surface of the Silencer's heatsink block. After this point, do not touch the mating surfaces with your fingers. Cleanliness here is very important. A bad thermal bond could shorten the life of your GPU.

Put a small blob of thermal compound on the raised inner square of the GPU. You need very little because the final coating should only be about the thickness of a piece of paper. I used a razor in the next step, forgetting how sharp they are. My wife says that the job's not done until my blood's been spilled.

Using the edge of a CLEAN razor blade or credit card, spread the compound evenly over the GPU inner square. Make sure it's not too thick (a piece of paper, remember?) If you have problems, clean it off and start over; there's plenty of compound in the tube.

When you're done, carefully inspect the compound and the heatsink mating surface for contaminants, such as a hair or bit of dust. Clean and start over if you find anything.

With the Silencer lying mating surface up, insert guides in the two screw holes to aid in alignment during assembly. A couple of 3/32" (2.4mm) drill bits worked for me. Turn the card over and align the holes beside the GPU over the drill bits. Lower the card onto the Silencer's mating surface, making sure that the old fan and the power wires do not interfere. Do not lift the card back up once it's in contact with the Silencer. If you do, you'll have to clean the thermal compound from both pieces and start over.

Holding the card in place, remove one of the drill bits. Align the metal beam so that any bent or otherwise modified flanges will be in the right position, then partially thread one of the screws into the hole. Remove the other drill bit, insert the other screw, and start its thread.

Turn the two screws alternately into the heatsink. As you did in the trial assembly, tighten the screws as far as you can without the beam touching any component on the board. Pick up the card/Silencer assembly and verify that the GPU lies perfectly flat on the heatsink and that the card and heatsink are firmly clamped together. You should be able to hold the assembly edgewise up to a light source and see a thin sliver of light between the heatsink and the outside edge of the GPU, but no light where the inner raised square of the GPU contacts the heatsink.

At this point I put little squares of electrical tape on the screw heads. This isolates the heatsink electrically and avoids scratching the aluminum bulkhead at the bottom of the card bay.

On to the Next Page - Installation in the G5.

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