I have had the same problem with my D600 - it needed to be flexed or pressed on the back before the power button would start the machine. This worked for some time, but then did not work any more. I thought then that I would investigate the actual reason for it, and so dismantled the machine. The power pressbutton switch is mounted on a small daughterboard, which in turn is connected to the motherboard via a multipin connector. I used a good lab microscope to examine the very small and fine solder joints which connect the line of connector pins to the motherboard solder pads. I found that many of these solder joints had developed extermely fine fatigue cracks due to relative movement developed between the daughterboard and the motherboard, such that these failty pins were no longer electrically connected to the motherboard. As the fracture in each case was extremely fine (but nonetheless completely separated) downwards pressure on either the power button and /or the back of the case under the connector, would close together the two halves of each broken solder joint, and thus re-establish the connections again, hence the machine would restart. When the pressure is released, the top of each cracked joint would then spring up a micron or two to re-break each faulty connection. As I said, I have proved this fault and directly observed the problem in action, under the microscope.
Now, as the pitch of the connector pins and the pins themselves are so tiny, it is not feasible to resolder the joints with normal soldering gear, which is way too big, meaning that many pins would be soldered together with a blob, rather than being soldered individually and not shorting to each other, as we need to do.
Not having the right type of soldering iron for this task, I actually made one up using my old Weller iron, using a hand-made tip fashioned from a 3mm brass screw with the head cut off, and the other end sharpeded to a very fine (sharp) conical tip. I atteched the brass screw to my iron tip / barrel with many turns of tinned copper wire, which I figured would also be a great conucter of the heat from the normal tip to the very sharp brass tip laced tightly to the side of the old tip. This worked a treat.
I need to say that if you are going to try this, you will need to work under a form of microscope, and you will need to have steady hands so that you don't burn any other parts, and can resolder each pin individually, without blobbing across to other pins. I found that using these tools, it was probably easier that I thought it would be, but you do have to be very careful and precise. I recommend that you do not use solder initially, but simply reheat (reflow) each joint while keeping some pressure on the the other side of the connector body, so that the joints are tending to close when the solder melts, to ensure each joint is individually remade OK.
I found that one of those small metal screwsrivers you can get in a cheap set (the smallest one in the set), can be sharpened up to a very fine point, to serve as a very useful "toothpick" probe. This can be used to gently clear any microscopic debris from beteen the solder joints so that there are no short circuits. If you happen to solder two pins tigether accidentally, you can easily clear the solder by reheating it for a very short time while using the "toothpick" to separate the molten solder again.
The probe can also be used under the microscope to gently probe the top of each joint in turn, to check the quality of your soldering. If the top part moves, relative to the solder pad, then the joint is still not OK (is still cracked), and needs more work. In this way, you can eventually be confident that all joints are solid, and also not shorting out to each other.
Remember - use only the minimum heating time for each joint, as you don't want to damage the motherboard or its solder pads (which might become unbonded with too much heat).
So - there you are. I have done it using this method.
Also, I recommend that you either do this, or get someone to do it for you, soon after you begin having difficulty with the on/off button, and you are having to apply pressure to get the machine to start. Why? Because the pressing fiix, while great, is actually applying more mechainal force to the connector joints, so that more will crack off. The danger is that as more and more force is required, all the pins will crack, and then the top of each joint will move across to short to the next adjacent joint, which could possibly destroy your motherboard.
Using this method, I now have resoldered the connector to its original condition. I have also carefuly adding some hot melt glue to make the connector body more rigidly connected to the motherboard (I did notice under the microscope that the connector body can flex quite a bit in its end mounts). Adding the hot melt prevents this happending, so that the repaired joints will not be fatigued off in future.
I hope that this helps all those with the same problem.
It can be done.
Aussie Fred
fred, June 2008
