Apple iMac (Original Flat Panel Model) Disassembly


Apple have had some funny ideas on cooling ever since the fan-less Apple III back in 1980 which suffered overheating problems resulting in chips expanding and popping out of their sockets (I don't know if it's true, but I hear Apple's fix for its customers was to drop the computer from a height of six inches in the hope the chips would re-seat themselves!)

Not that the flat panel iMac has a problem with cooling as such. It is an unusual design though and great care must be taken in the reassembly or you will have a problem with thermal damage.

Most computers have a hefty heatsink and fan fitted firmly on top of their processors to prevent them overheating and burning out. The iMac FP is different. As with a lot of other Apple machines, there is no processor fan, just a large cooling fan at the top of the domed case. In order to keep the heat-generating components cool, the iMac FP has a thermal pipe in the upper section of the case dome. When the machine is bolted together, the thermal pipe is in contact with certain components on the logic board so that it can transfer heat away from those components during operation. When disassembled, the conduit is no longer in contact, thus you should never power one of these units up while it is opened.

You must also be very careful on reassembly. The contact points between the components and thermal pipe must be cleaned of old heat transfer grease and new grease must be applied. To ensure proper contact between the thermal pipe and component surfaces, the screws holding the case together must also be tightened to at least 17 in.-lbs which is... uh... 304kg/m (I think) in proper terms. Failure to do all this may well result in your reassembled iMac FP frying itself requiring a whole new logic board at great expense

You have been warned!

You'll need Torx screwdrivers for disassembly.

Look out ! It's a disclaimer:
Unless you're a dab-hand with a screwdriver, don't attempt any of this. Messing around inside your computer could cause damage and in certain cases can be hazardous to your health. This page is just a guide - you follow these instructions at your own risk. You should be careful handling the internals of a computer and follow antistatic precautions or you may cause damage.

1. Place the unit face down with the screen resting on something soft such as a cloth. Undo the four screws on the user access plate (underside). These screws are captive so they won't drop out. Remove the plate by pulling at the loosened screws.

2. Here we have the Airport Slot (A), the Memory expansion slot (B) and the PMU button (C). If upgrading the memory use a PC2100 (DDR266) SoDIMM. The PMU switch is a tiny button under the flexible partly transparent plastic cover. Pushing this button once for half a second will reset the power manager (always worth a try if your iMac FP is not powering up). Power managers can be locked up by mains power fluctuations. Don't hold the button in for too long and don't push it more than once or you may end up with more problems.

3. Here's the part you shouldn't attempt unless you have some heat transfer grease handy. Removing these screws carries the risk of damaging your logic board. If you want to proceed, rotate the base so that the CD drive is on the right (as this reduces strain on the internal cables when the case is opened) and take out the four torx screws. When reassembling, these screws need to be tightened to at least 17in.-lbs. If you don't have a torque driver you can hand tighten them until they are nice and tight - but don't over-tighten them!

4. Gently pull away the lower section of the case. You have now separated the logic board from the heat transfer pipe. Don't attempt to power your unit up or it will be damaged. The P-RAM battery is at the bottom of this picture. Notice also that the factory fitted memory is a standard PC2100 DDR266 DIMM. If you wanted to upgrade the memory of your iMac FP and you don't want to fit a SoDIMM into the underside slot shown earlier, you can fit a higher capacity DIMM into this slot.

5. These are the points on the logic board that need to be cleaned and re-greased before reassembly.

6. Points on the upper case that need to be cleaned and re-greased.

7. For drive removal, undo the six screws.

8. The PSU is split over two parts. Undo the screws to remove it (you will have to flip open the CD door to gain access to two of the screws). The screws under the CD door are shorter than the other screws. If you fit the longer screws into these holes on reassembly then you will cause damage viewable on the outer case.

9. Remember to apply new heat transfer grease and tighten those screws properly on reassembly!


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