How to: Replacing Cooling Fans and Thermal Compound on a Video Card

 

Replacement Parts

HD7970 Fan Repair 018Out of its shroud, we can take a look at the back side of a fan to read the label. In this case we can see that this fan is a Everflow Model T128010SM, 12 VDC, and draws 0.20 Amps. Interestingly, but not necessarily helpful, we can also see the fan was manufactured in April of 2013, making it about 3 years old.

Typing the manufacturer and model number into Google we can see the exact replacements are available on Aliexpress for about $3.20 each if I buy 5  or more. This isn’t a problem as I would probably order at least 10 since I have other cards with these fans, but I don’t want to wait 30 days for shipping from China for my out of commission card.

GPU_Fan_Info

Fortunately, the description contains other important details about the fan, namely the size and mounting hole spacing. Looking at the description above, we can see that the fan dimensions are 75 mm x 75 mm x 10 mm, and that the mounting hole spacing is 40 mm x 40 mm x 40 mm, center to center. It is also a 2 pin connector, which was obvious from looking at the old one.

HD7970 Fan Repair 016Using this information, I set out to find a equivalent one on eBay that is hopefully located in the US, and came across a replacement fan that met all of the correct dimensions and power requirements, but is a 4 pin version. These 3 and 4-wire fans usually include a sense pin and possibly a PWM control, but if these wires are not connected they work equivalent to that of a 2 pin fan.

The table below illustrates the different pin-outs. Notice that pin 1 (black) is ground in all cases.

Pin
Mini PWM

(4 pin)

PWM

(4 pin)

Fan w/sense

(3 pin)

Fan

(2 pin)

Signal
1 black black black black ground
2 yellow red red red +12 V
3 green yellow green (yellow) Sense/Tach (RPM)
4 blue green PWM (fan control)

Since I can purchase these fans for about $5.00 each, shipped from California, and they otherwise fit the bill in size and hole spacing, I am willing to do a bit of wiring to speed the process up. I will order 10 exact fit replacement fans from Ali Express for future failures, but I am also going to order 4 of these “close enough” replacements off eBay for quicker shipping.

Cleaning

HD7970 Fan Repair 009

With the shopping out of the way I can get back to preparing the heat-sink and GPU board for reassembly. The image to the left shows the heat-sink half with some residue thermal compound on the area that comes into contact with the GPU core.

Surrounding this area are several thermal adhesive pads that cover the memory chips. These pads are adhesive on one side only, which is the side attached to the heat-sink, and are positioned so as to cover the top side of the memory chips in order to help dissipate the heat. You can obtain thermal pads readily online, but these still are in good shape and are already positioned properly and the right thickness, so a quick clean up and they should be good as new.

First find a suitable scraper (don’t use anything metallic) such as a old credit card cut in half, a guitar pick, or something similar, to loosen and scrape off as much of the old thermal compound as you can. Leave the thermal pads alone for now, we are just working on the residue compound in the center. Don’t worry about getting it shiny just yet, we just want to remove the high peaks and lumps to make the next step a bit easier.

When you have most of the bulk of the leftover residue gone, vacuum or blow off any excess material. Now we will use a dampened lint free cloth or cleaning pad moistened with 99% isopropyl alcohol (available at drug stores) to gently wipe away the remaining residue. If you are having a hard time finding 99% isopropyl alcohol, 91% and 70% are commonly available and will also work, but these can leave a residue affecting later application of new thermal compound. This process may take several iterations using new cleaning cloths or pads each time, but when you are done the surface should be clean and shiny.

Repeat this same procedure on the PCB side of things, paying extra careful attention to the actual GPU area. Take your time and be sure to blow out the dust and buildup as you work. I don’t recommend vacuuming this side, as static electricity buildup can be a real concern. Simply alternate wiping with slightly (alcohol) damped cleaning cloths and turning the card over (over a garbage can works well) to dump any loose material out, and then blow canned air over the area to clear out loose gunk. This will probably take some time, but be patient and thorough.

 

HD7970 Fan Repair 007
All cleaned up and ready for a date with some Arctic Silver 5 thermal paste.

 

Pay very close attention to the small components surrounding the actual GPU, as they can be damaged easily by even slight physical touch. You also do not want any old (or new) thermal compound on these at all. Although all thermal compound is (obviously) thermally conductive, most are not electrically conductive. However, they can become somewhat capacitive in nature, which if the components were to be coated in the thermal compound, may cause problems.

Arctic Silver Warning Label

I cannot stress this enough, but just remember that a gentle tough is required all around on this part of the process. If you find yourself become impatient, simply walk away for awhile and come back to it later. This is definitely one area where an ounce of prevention is worth a pound of cure, or in this case possibly your entire GPU.

Also, when finishing up cleaning the GPU area also go gently over all the memory chips (12 black squares surround the GPU in the image above) with an alcohol moistened cloth to remove any buildup. These should only require a once over, followed by a quick blast of canned air to remove any residue or lint.

As shown in the image above, the surfaces of both the GPU and surrounding area should be free of visible residue and other dirt, oil, or fingerprints. While the heat-sink portion should be clean, the actual surface of the GPU chip should be a literal mirror finish, at least on the HD 7970’s. It does not come out clearly in the photo, but it is very mirror like when looking at the surface. If you cannot see yourself in it like a mirror when you are all done, you did something wrong.

On the next page we will begin the reassembly…

 

2 Comments

  1. Nice article! I had to mod the frame on a pair of 92mm fans with pwm to fit my card and found your article looking for the pinout of pwm fans. You make no mention about the thermal pads needed for the ram chips, i found they seem to be recommended to keep mem temp on check.

    • Thanks for the comment.

      Yes, the thermal pads are indeed important and for the most part I just clean them off with a quick wipe of a alcohol moistened cloth and leave them be.

      While there are after-market replacement pads available, in most cases the originals will continue to work just fine assuming they are not damaged in any way and continue to make contact with the heatsink once it is reattached.

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