More than few educators and ScienceMan readers have emailed regarding strange iMac DV behaviour - this is manifest as mysterious shutting down or starting up, or the inability to shut the computer down. This is not necessarily a hardware problem - many times throwing out the energy saver preferences file will solve the problem.

But there does seem to be a problem with the first generation of iMac DV computers - these are the slot loading ones that came with the old keyboard and "hockey puck" mouse. The power button under the monitor is poorly designed and gets jammed easily, especially when subjected to rough use in the classroom. So what exactly is the problem?

To make a long story short, the button gets jammed in its socket. This may be due to several problems - an oversized button, a misaligned light inside the button, or a spring that is just too weak - or a combination of all three! How can you tell if you button is jammed? It will probably be inside the socket instead of flush with the computer surface, and it will offer no resistance to pushing. The follwing is a movie (QuickTime) of a jammed button:

For contrast, here is the (well-designed!) button in action from a newer iMac DV model - these are the machines that sold with the newer keyboard and mouse. This button is working perfectly:

So how do you fix this problem? Considering the age of these machines, it is unlikely you have a warranty, but f you are under warranty, of course, take it in to an authorized service provider because you'll void the warranty if you open the case yourself. The following is a series of untrained, handyman tips for fixing the problem - proceed at your own risk!

First, you'll have to remove the bottom of the iMac. Turn it upside down on a soft surface, and find the screws to remove, there are 4 of them. The first two are easy to see, they are right by the fold out stand:

But the other two screws must be accessed by first removing the plastic panel that is covering the VGA port - once you have removed the plastic cover, make sure you remove the outer screws holding the case, NOT the inner two screws:

Now you can remove the bottom of the case - start at the back, and lift the bottom cover toward the front, be careful, don't break the clips at the front:

Looking inside the removed cover, you can see that the button is really just an outer button - and it is not the problem. The problem is with the inner button:

Look at the gap in the chassis behind the button, and you'll see two small tabs holding the button in - you'll have to use a small flat screwdriver to push these clips in toward the button in order to remove it (the button will come out the front). Careful, there's a spring that may fly out!

You'll notice the light in the upper photo - it has been suggested by some that the misalignment of this light causes the button to jam. If it appears bent to one side, up or down, put it back in the center position.

The spring is a weak little thing - I recommend stretching it out a bit (optional! - you may want to try this if the button still gives you problems) so that it will have more resistance. Be careful, you don't want to distort it terribly so that it won't fit back in.

That brings us to the major culprit - the oversized inner button. You'll need some fine sandpaper to grind off an even half a millimeter or so from the outside of the button:

Once you've done this, put the spring back into the button and push it back into place. Note that the button has tabs so it will go in only one way. Test the button to see if it works reliably and smoothly without jamming. You're done!

Even though this does a good job at fixing the button - once you've got it working, I strongly recommend avoiding the use of this button (many Apple service providers recommend the same thing). Use the button on the keyboard instead. If you can, clearly indicate to students that this button is off limits - a sticker perhaps?

If you have comments or suggestions to help with this fix, please send them in and we'll add them to the tutorial.