Need to get to the motherboard of one of these things? If you want to change the P-RAM Battery or memory then you do. It's not too difficult - fiddlier than the later revision iMacs. If you're not sure what type of iMac you have then here's a few pointers....
The Revision A came only in Bondi Blue flavour;
The Revision A has an InfraRed port on the front left speaker;
The Revision A has a tray loading CD Drive rather than a slot loading CD/CDRW/DVD Drive;
The Revision A was the first iMac (released 1998) and used a CRT screen (so we're not talking about one of the fancy flat panel jobs here)....
...and here's some good news for you later revision CRT type owners, if a memory upgrade is all you want to do, flip the thing over and you'll find a door on the underside that can be opened with a flat bladed screwdriver to reveal two 168 pin DIMM PC100 memory slots.
The Revision A uses SoDIMM memory (the same type as used in some laptops).
Okay, boring disclaimer follows.......
It's important to note that messing around in any electrical device is dangerous. If you are not technically minded or confident in your abilities, don't go removing any screws. These instructions are just a guide - you follow them at your own risk. You should also be careful handling the internals of a computer. You should follow antistatic precautions or you may cause damage.
And now that's out of the way it's time to break out the screwdrivers.
1. Disconnect all cables and carefully place the computer onto it's screen (you might want to put a cloth down to prevent scratching the screen). Undo the screw at the top rear of the unit.
2. Gently use a flat blade screwdriver to separate the lower half of the white translucent case from the white translucent strip above it
3. Grip the lower translucent cover and pull it up and out to remove it.
4. Undo the two screws (arrowed)
5. Unscrew the cable grip
6. Disconnect the two signal cables
7. Disconnect the two power cables
8. Grip the metal handle at the top and pull out the motherboard/drive assembly
9. The motherboard/drive assembly removed from the case
10. Pop off the top battery cover to gain access to the P-RAM battery. If replacing it you will need a 3.6v 1/2 AA Lithium battery - and be sure to get the polarity correct upon reinsertion (use the picture below for orientation if you're unsure). You can purchase a replacement battery from here.
11. To access the memory pop off the metal grill. The Revision A has 32MB on the motherboard and can take an upgrade SoDIMM in this slot. Don't get confused with the other SoDIMM slot on the motherboard - this is for V-RAM (i.e. a graphics memory upgrade).
12. For further disassembly, undo the four screws on the upper case clam and the two screws in the transparent part of the case above the fan. You may need to remove the side access trap door to remove one of the screws.
13. Using a flat blade screwdriver prise the lower half of the case from the upper case clam
14. With some tweaking the lower half of the case can be removed. Beware of the two plastic clips either side of the CD-ROM drive - it's easy to break these off as you remove the lower case.
15. Undo the two front screws.
16. Use a flat blade screwdriver to unclip the screen surround from the blue upper clam shell.
17. Use a small flat blade screwdriver to remove the two plastic screw covers from the top of the case and then remove the two screws.
18. Push the sides of the blue rear clam shell upwards and pull it away.
19. To gain access to the circuit boards, first remove the two top screws on the shielding.
20. Then remove the eight screws on the side shielding (four on each side).
21. The PSU board (left) and analogue board (right) can be removed by disconnecting any attached cables and removing retaining screws.
22. Reassembly is the reversal of disassembly!
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