New Logic Board, missing GPU heat sink

[Dennis Nedry]

I use my pismo extensively. It started shutting off randomly, and I narrowed it down to the logic board by swapping parts with another Pismo.

I ordered a new logic board on eBay and it is definitely brand new, never used. The problem is that on the bottom, on my original board, there is a small heat sink on the ATI Rage Mobility 128 GPU, and on the new one there is NOT.

I assume that I am supposed to somehow peel the heat sink off of the old logic board, buy some expensive thermal adhesive, and glue it to the new one.......... AHHHHHH I wanted to have my Pismo back TODAY!

So I got to thinking, which may be a dangerous thing. The heat sink is not very big, and OS X doesn't particularly utilize this chip. No graphics acceleration takes place I've heard. I'm sure it does do some stuff, but I doubt it works particularly hard.

So who thinks it would be possible to run this WITHOUT the little heat sink? The adhesive costs more than another new logic board.

 

[Osgeld]

mix some thermal paste with gel super glue

it is kinda brittle once dry but it took a hammer to knock it off the last gpu i tried it on (last time I used some silver stuff on a geforce 2, it did not come off until I whacked it, didnt damage the chip but user be warned)

 

[johnklos]

I know you're anxious, but if you can wait, you can buy some epoxy-type heat sink compound and put the heat sink on permanently. I use it for putting heat sinks on my m68040s on my QuadDoublers and I've used them to put graphics card heat sinks / fans on iMac G3 CPU cards, like so:

It's worth it.

 

[Osgeld]

well since were showing pictures, here's the heatsink I last did the super glue trick on, It ran on a hot-rodded geforce 2 GTS from 2004 to 2009, I was moving, tried the card, it was finally doa so I (lightly) wacked the heatsink with a hammer (once) and poped it off by hand, It was scavanged from a intel 486 overdrive chip (long ago dead), and the power wire is a moded wake on lan cable

I agree it is no replacement for proper thermal epoxy, and I have no idea how it would hold up under mobile conditions over time, altho i was not exactly kind to the card this thing was attached to, the board had warped so bad from severe overclocking / heat of the non gpu items (dac ram power) that it would not operate while bolted down, and if you were ever silly enough to shut off the computer it would require vigorous wiggling (usually done blind by gabbing the monitor cable) for quite a aggravating while before hitting a magic spot in the agp socket + case/bracket friction to post (i did this for a quite a few years)

so the method does hold up to some bull

 

[Dennis Nedry]

Does anyone have any idea why these would have NO heatsink, though? They are brand new, and there is no residue of any heatsink ever having been installed. The seller on eBay says that his whole stock doesn't have any heat sinks. He suggested that maybe this particular revision of the board didn't require a heat sink on the GPU. I'm not too sure about that; GPUs get pretty hot, especially a 3D one, ancient as it may be.

I don't know what to think I guess. These clearly never had a heat sink, and it's impossible to remove the one that's already stuck onto the bad board. I have 2 of these. I tried to remove one (nothing to lose) and it instantly shattered. Impossible to remove in one piece without some solvent or heat gun.

I thought maybe the heat sinks shipped separately and were adhered on site to avoid weakening during shipment?

I just want to know what the heck happened here if anyone has any ideas.

 

[Mars478]

Pretty sure a new logic board is sold without any heat sinks. Could you post a picture of the GPU Heatsink?

You could make a makeshift heatsink... Or just buy another Pismo one.

 

[Dennis Nedry]

Here is a picture of it as seen in the Apple Service Manual:

This is from page 91: Take Apart/Procedures/I/O Logic Board/PCMCIA Card Cage.

You can see the shiny adhesive pad that holds it on. There are no screws or clips.

Mars487: If you know that new ones came without this heat sink, what were service people supposed to do? Leave it without a heat sink or somehow transfer the old one to the new logic board?

 

[Dennis Nedry]

Here's a picture of one of my faulty boards:

 

[Mars478]

I don't know anything about the pismo, but apple is strange like that.

Have you tried removing the heatsink with a heat gun?

 

[Dennis Nedry]

I don't know anything about the pismo, but apple is strange like that.Have you tried removing the heatsink with a heat gun?

I thought about using a heat gun, i.e. one for removing paint, but the tube of adhesive to attach it to the new logic board is basically more expensive than to just buy another board that already has the heat sink.

This all really puzzles me though. I don't know what to make of it. There's no way that Apple service technicians would have been expected to remove the old heat sink and reuse it.

The only thing I can think of is that new logic boards came with new heat sinks that just needed to be "peeled off" and stuck on.

 

[Osgeld]

yes it most likely came as a service pack

 

[Dennis Nedry]

yes it most likely came as a service pack

I agree; that really is the only way that makes sense.

That's strange too though because there are no instructions in the service manual for attaching the new heat sink either! Maybe they just included instructions in the packaging.

Or maybe these boards are from the last run and they RAN OUT of heat sinks! Who knows.

 

[Dennis Nedry]

mix some thermal paste with gel super glue

[...]but the tube of adhesive to attach it to the new logic board is basically more expensive than to just buy another board that already has the heat sink.

Sorry Osgeld, I neglected your recommendation. This is a neat idea and I may try it.