Lapping advise please (RSX chip on PS3)

I've tried using a really thick layer of AS5 and the centre still doesn't make contact, so this isn't an option. This is the final solution :p:eek:
 
How can it not make contact? The only way I can think of is if you're not putting the grease on the chip itself.

Put a great big dod of the stuff in the sunken bit on the chips IHS.
 
Obviously that's going to work, but it's not going to cool the chip very well is it?

Sumanji said:
I did do a little experiment though. I spread some AS5 on both the Cell and RSX chips in a thick coat, and then "etched" a criss cross pattern into it with a paper clip. I then mounted the heatsink on as tightly as I could and left it for a while. When I removed the heatsink I found that the criss cross pattern was still clearly present over most of the central area of the RSX chip. I.e. the heatspreader is probably concave and making crap contact :(
Click to expand...

That's how I initially figured there was no contact (obviously did the torch light test before that).

Cheers,

Suman
 
it doesnt matter if the thing ends up not very flat. so long as the center, where the cpu is, ends up higher than the edges the heat transfew should improve over only the edges contacting.

fortuneately lapping by hand causes exactly this profile - low edges high middle.

before you start arguing - consider bowed waterblocks..
 
lol nope, I'm back at my parents' place for Xmas, and still need to go out and get sandpaper etc. I take it 1000 grit upwards won't be easily available from B&Q etc?

Cheers,

Suman
 
Sumanji said:
lol nope, I'm back at my parents' place for Xmas, and still need to go out and get sandpaper etc. I take it 1000 grit upwards won't be easily available from B&Q etc?

Cheers,

Suman
Click to expand...
No worries. Have a nice xmas. :)

As the others have said - Halfords should have some.

gt
 
Hey guys,

I finally started my little project today :D Starting out with the heatsinks; I've used the "razor test" and found out that my RSX heatsink is ridiculously concave, so I started lapping. Currently about half way through with the 240 grit sand paper and here's what it looks like:

2iiza0g.jpg


As you can see the circular area in the centre is still the original darker shade of grey, as it's barely been touched by the sandpaper. The Cell heatsink seems a lot flatter, but I'll lap that as well after this. If the contact is still crap after that, I may have to lap the heatspreaders on the chips... this will be very risky (as well as annoying). Will keep you updated with pics!

Cheers,

Suman

P.S. If this doesn't work I will be very :mad: !!
 
I've fixed one that had the exact same problem as this, but not sure it was concave in the same way, I added 4 washers to the screws for the heatsink and tightened the screws as far as they would go. Pulling the heatsink tighter onto the chip itself. Might be an idea you can use :)
 
Hey Bobby,

Can you explain in a little more detail what your problem was? What gave you the idea to use washers, and how did it work out?

Cheers,

Suman
 
Well I've always used washers to fix xbox 360's. Wasn't my ps3 I done it too, basically no matter what I done, be it clean the fan/heatsink, re-apply thermal paste and re-fit the heatsink the paste barely made contact with the heatsink.

So added the washers to the bolts that hold the heatsink in and it just allowed for me to pull the heatsink down tighter by over-tightening it.
 
Is that heatsink attached to something else? (the copper pipes in the picture, where do they go?).

I think this will be worth it, certainly seems like that heatsink did not have good contact with the chip!
 
just an idea as you wanted too do the RSX chip but its stuck to the motherboard why dont you get a little hand held mirror that should be nice and flat and glue your sand paper to it ? its just a thought :)
 
xiphrex said:
Is that heatsink attached to something else? (the copper pipes in the picture, where do they go?).
Click to expand...

Yes mate, they're attached to the actual fins. You can seem in the pic below (which is after about half an hour with the 240 grit - my hands hurt :( )

v5e5n9.jpg



Mr. May said:
...why dont you get a little hand held mirror that should be nice and flat and glue your sand paper to it?
Click to expand...

Legend :D why didn't I think of that?! Thanks dude!

Suman
 
That looks good man.

You might find those pegs on the fins are what is giving you bad contact, so you might need to sand those down as well. Check it on a flat surface, if the thing isnt straight on there but at an angle down towards the chip then it might be those pegs being too long.
 
Hey,

The pegs fit into holes in the motherboard I think, so shouldn't be a problem :) well here are my results... only went up to 1200 grit so not super shiny (although I thought it would be at least slightly shiny?!). Much flatter than before:

600 grit:

6qxtn6.jpg



800 grit:

2ytwgv6.jpg



1200 grit:

2vwep3t.jpg



Will go and buy a pocket mirror tomorrow and do the rest!

Cheers,

Suman
 
I remember from the NF7-S days when people were lapping their NBs, I just used a square of sandpaper spray mounted to the bottom of a lapped heatsink, worked a treat!!

Mikey
 
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