Applying thermal compound to SXPS 1645

For those of you who replaced the thermal paste on the CPU in your SXPS 1645, could you help me out a little bit?

I've never applied thermal paste to a CPU before. When I first got my laptop, I decided to try it. I looked at the Dell service manual ( here) for the 1645, which just redirects you to the 1640 manual. I thought there were some motherboard changes between the two (the northbridge was consolidated or something or other), but I guess it's similar enough.

Here are the steps in case you don't feel like clicking through to the service manual:

1. Follow the instructions in Before You Begin.

2. Remove the base cover (see Removing the Base Cover).

3. Remove the rear caps (see Removing the Rear Caps).

4. Loosen the seven captive screws that secure the processor heat sink to the system board.

5. Lift the processor heat sink off the computer.

1-3 are easy enough. But Step 4 says there are seven screws that need to be loosened. There's even a picture showing their locations. It's been a month or so since I've tried this, but I remember there being more than seven screws. Also, the screws weren't in the same places as in the picture.



I haven't done this before, so I'm following this manual very closely and then this discrepancy came up and it worried me a bit. But I went ahead and loosened all the screws I thought were necessary (maybe 10 total?).

The next problem is Step 5. This is probably very stupid of me, but I couldn't lift the thing up because a wire was in the way. I wish I had a top-down view so I could show where it was. But if you look at the picture, the wire starts just barely to the left of the bottom-left corner of the fan, goes about three quarters of the laptop's length, then curves around to the right and eventually emerges near the CPU and then connects to something. Since removing the heatsink requires lifting up the entire copper pipe thing, and the wire runs over part of the pipe, I can't lift it up. This part really confused me and I wasn't sure how to deal with it, so I gave up and decided to wait a month or so when others got their laptops and knew what they were doing.

Recap:
1. Once I have the base cover removed, how many screws need to be loosened on the heatsink assembly?
2. How do I deal with the wire that covers up part of the pipe?

I won't be able to try again until tomorrow afternoon or later this weekend (hopefully tomorrow but it depends on if I get a reply).

Thanks for taking the time to read. There are so many smart people in this forum and I hope you'll find the time to help me out.

Is it bad that I'm studying to be an electrical engineer and can't figure this out?

 

I just remembered something. I did a forum search and I only found one thread specifically about the 1645. http://forum.notebookreview.com/showthread.php?t=445940 . I didn't have this when I tried the steps a month ago; I only just found it.

I'm not interested in replacing the thermal pads or applying thermal compound anywhere other than the CPU (unless it turns out to be really easy to apply it to the GPU), so maybe not all of that thread is relevant here. But if you scroll down to post #7, there are some great pictures there.

I noticed that this person removed the fan as well as the heatsink assembly, which is different than the picture I posted above shows. Do you have to remove the fan? When I tried this a month ago, there was black tape over part of the fan and what is shown being lifted in the picture above and I couldn't just the lift out the black thing by itself (presuming I could make it that far); the fan would have to come with it. From the picture in the thread I linked to shows, it seems like he had the same issue. I guess this is just an error in Dell's manual? Seems like a bad place to have an error.

I'm not sure if I was even trying to ask a question here...
Oh yeah, the difference between the number of screws that have to be loosened.

 

10 screws total. For the wire, you'll notice it's inside a trench, just use your screw driver to get it out of the trench and lift it up starting from the back heatsink area up to the wireless cards. The cable can't easily be disconnected, but lifting it out of the trench gives you plenty of space to remove the heatsink. The extra screws to remove on the heatsink are marked in red on this image:

 

The GPU is exactly the same as the CPU for applying thermal compound, do both while you have the heatsink off. You'll have to clean both anyway and apply something once you break the seal. Yes you remove the fan. I don't recommend removing the soft pads used for the chipset/ram/etc - only the GPU and CPU.

 

Wow thanks for replying so quickly!
I will try this tomorrow afternoon and post back with the results.

Thanks again!

 

I got it done yesterday. Took a while (longer than it probably should have), but I was trying to be careful about the whole thing. I replaced the thermal paste on the CPU and GPU, but didn't mess with the pads. Everything went smoothly. Of course, I forgot to test the temps before I made the change, so I don't know if I made an improvement or not. My CPU temps vary between 40 and 55, so I guess that's reasonable? I'm not sure what they were before. I haven't done any gaming on this laptop yet, so I don't know how high the temps will go. Most I've done is watch a 1080p youtube video. Oh yeah and I used MX-2. I've heard a lot of good things about AS but I was afraid of what might possibly happen if I accidentally got some of it other than the CPU and GPU. Also, I usually have a laptop cooler connected, so I'll see if that makes a difference when I get back to it.

Thanks again for your help.