Reassembled XOs fail heat spreader test

[Samuel Greenfeld]

The "unused" hole actually is filled by one of the screws which holds in the
rear plastic panel.  That's why the screw holes which only secure the heat
spreader have arrows pointed at them.

The fanciest (newest?) XO-1.5 heat spreader design I've seen adds a support
bar up to the green screw hole above near your area of concern, again filled
by a screw used to secure the back cover.  I'm not certain though if this is
the design John is referring to, but I have seen a few XO-1.5s with it.

It may be possible to bend the existing heat spreader in a certain manner
which solves the problem.  But I would *not* be someone who could recommend
this approach for deployments.

Some of OLPC's hardware engineers may be traveling this weekend, so I'm just
trying to provide you with a quick explanation in the meantime.



On Fri, Jul 22, 2011 at 9:55 PM, Sridhar Dhanapalan
<sridhar at laptop.org.au>wrote:

> All of the XOs I've seen have three screws on their heat spreaders.
> I've attached an annotated image. Hopefully the lists don't strip it
> out.
>
> There is an unanchored screw point in the bottom-left. However, the
> danger area is at the top, particularly in the top-left. This affects
> contact between the heat spreader and the Companion Chip, and might
> also be affecting contact with the CPU. Do the four-screw versions of
> the heat spreader address this problem?
>
> Thanks,
> Sridhar
>
>
>
> On 23 July 2011 01:21, John Watlington <wad at laptop.org> wrote:
> >
> > Do your heat spreaders have four screws or three ?
> >
> > The final heat spreader for XO-1.5 production had four screws
> > holding it down, to ensure a good fit.    If your heat spreaders
> > only have three, OLPCA should be able to get proper replacements
> > from Quanta.
> >
> > Regards,
> > wad
> >
> > On Jul 22, 2011, at 10:35 AM, Sridhar Dhanapalan wrote:
> >
> >> We are currently engaged in changing the motherboards in over a
> >> hundred XO-1.5s. In many cases, the XOs are failing the heat spreader
> >> test afterwards.
> >>
> >> However, we can get the test to pass if we press down on the lid,
> >> behind the screen. This suggests to me that the heat spreader is not
> >> in proper contact with the chips.
> >>
> >> Without the lid plastic affixed (heat spreader exposed), we can see
> >> that the spreader is not touching the chips properly. We have tried
> >> bending the metal slightly near the screw points, but the contact
> >> doesn't last.
> >>
> >> Is there any way that we can deal with this better? We are changing
> >> the motherboards in these XOs because they have succumbed to
> >> overheating. I want to avoid that from happening again.
> >>
> >> Thanks,
> >> Sridhar
> >>
> >>
> >> Sridhar Dhanapalan
> >> Engineering Manager
> >> One Laptop per Child Australia
> >> M: +61 425 239 701
> >> E: sridhar at laptop.org.au
> >> A: G.P.O. Box 731
> >>      Sydney, NSW 2001
> >> W: www.laptop.org.au
> >> _______________________________________________
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> >> Devel at lists.laptop.org
> >> http://lists.laptop.org/listinfo/devel
> >>
> >
> >
>
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