Lapping advise please (RSX chip on PS3)

Sumanji · 6 Dec 2008 at 21:43

Lapping advice please (RSX chip on PS3)

Hey,

Long story, but after a bit of experimenting I've found that the RSX chip on my PS3 is very concave, and does not make any contact at the centre. This is causing the console to overheat and make a lot of noise, so I want to try and lap it to make it flat.

Now I've read a few lapping guides, and have a fair idea of what to do. The problem is all of these guides had a mobile item being lapped - i.e. the CPU/heatsink is moved on sandpaper which is taped to some glass. The RSX chip however is soldered to the motherboard, so my only option is to rub something against it whilst it is in a fixed position.

What sort of object could I use to keep the sandpaper (and chip I supposed) perfectly flat? And how would I avoid bit of metal falling onto the motherboard?? Any advice appreciated!

Cheers,

Suman

Bradley8988 · 6 Dec 2008 at 21:46

A small bit of 8 or 10mm acrylic I guess. I would just get it replaced under warrenty or maybe use a thermal pad instead.

Sumanji · 6 Dec 2008 at 21:57

Ok cool... not sure where I would get such a small piece of acrylic from though?

It's about a year out of warranty unfortunately

tried the thermal pad route, but it does not make any contact at all in the centre! (Akasa Shin-etsu)

Cheers,

Suman

DigitalReaper · 6 Dec 2008 at 22:15

Maybe you could modify the heatsink to fit the chip instead. File/sand away the edges to make the centre stick out a bit.

Or maybe put a small peice of metal (e.g. a real copper coin) in the centre with a pad on either side of it to fill in the gap. Modern 1p/2p coins are some sort of alloy, you can check by sticking it to a magnet. A real copper coin won't stick. You'd probably want to file both sides flat first though. (this is my 4th or 5th edit now... I really need to think more before I hit save :rolleyes:

)

Sumanji · 6 Dec 2008 at 22:23

Hey,

Not sure exactly what you mean about the coin - won't it be far too thick to have any balanced effect?

Cheers,

Suman

DigitalReaper · 6 Dec 2008 at 22:29

Isn't the core of the chip in the centre? Thats all you really need to cool.

Bradley8988 · 6 Dec 2008 at 23:45

it's like a washer mod they do. Find a copper coin and shape it and smooth it then sandwich it between chip and hsf

Sayso · 6 Dec 2008 at 23:46

dont do it

UberGT · 7 Dec 2008 at 00:19

I wouldnt lap it if it was soldered on the board to be honest, get it replaced under warrenty.

TheRedZealot · 7 Dec 2008 at 00:23

DO IT DO IT DO IT!

MikeHunt79 · 7 Dec 2008 at 00:30

UberGT said:
I wouldnt lap it if it was soldered on the board to be honest, get it replaced under warrenty.

This

Sumanji · 7 Dec 2008 at 01:23

UberGT said:
I wouldnt lap it if it was soldered on the board to be honest, get it replaced under warrenty.

MikeHunt79 said:
This

Sumanji said:
It's about a year out of warranty unfortunately...

Sayso said:
dont do it

Why not?!

Bradley8988 said:
it's like a washer mod they do. Find a copper coin and shape it and smooth it then sandwich it between chip and hsf

Ok... but surely adding another 2 layers of interface won't really help thermal transfer? I've seen people who have lapped the Northbridge heatspreader on their motherboards, so this isn't really that much diferent...

Cheers,

Suman

sebna · 7 Dec 2008 at 09:24

M8 I got bad news for you. You wont be able to lapp it if you can not put it on flat surface as all guides show you. The reason is simple your hand can not tell when it is flat so you would lap some nice nowhere near to flat shape (probably even worse contact than you have now).

But as some one suggested you can work on heat sink.

Good luck

UberGT · 7 Dec 2008 at 11:57

seems you only have 2 chioces, lap it with a small piece of glas and some wet and dry or mod a heatsink, if your going to lap it you need to think of a way to remove the metal shavings i.e a hoover or something whilst your doing it, its going to be risky but obv its useless unless you do something, can you not get motherboards from the bay of E?

gurusan · 7 Dec 2008 at 12:29

Do you have a pic of the CPU?

I'd just use some extra thermal paste tbh

Sumanji · 7 Dec 2008 at 14:05

Got a cool idea from a dude over at XS:

HKPolice said:
Take a small piece of metal like an old Socket 7 heatsink, lap the base until it's a mirror. Cut a piece of sandpaper until it's the size of the base of the heatsink but with 2 opposite sides longer. Put heatsink on the sandpaper, fold the 2 longer ends upwards and you've got a nice sander for the chip. Don't worry about any metal particles, just use compressed air.

As for the metal shavings, I was going to use electrical tape all around the socket to kinda seal it up, and then tape a large anti-static bag with a hole in it all around to catch any of the particles. I can run the old Dyson over it when I'm done to mop all the crap up

Cheers,

Suman

UberGT · 7 Dec 2008 at 14:40

Sumanji said:
Got a cool idea from a dude over at XS:

As for the metal shavings, I was going to use electrical tape all around the socket to kinda seal it up, and then tape a large anti-static bag with a hole in it all around to catch any of the particles. I can run the old Dyson over it when I'm done to mop all the crap up

Cheers,

Suman

Sounds like a plan let us know how it turns out.

Sumanji · 7 Dec 2008 at 14:59

Will report back with n00d pics

This is my last effort trying to silence this PS3, otherwise it's off to the shops to get a 65nm model

gt_junkie · 7 Dec 2008 at 15:42

Good luck!

Can't wait for pics!

gt

The Halk · 7 Dec 2008 at 15:54

Use masking tape rather than electrical tape (masking tape is white stuff that peels off easily, used when painting).

The poster above who said you will struggle to get a flat surface is correct.

I'd instead just use far too much thermal grease. It's not as if you're trying to nudge it down by a couple of degrees to get that killer overclock.