Regarding IR-CUT Filters - I've heard that giving the camera a good wack also works sometimes, but some common sense and judgement as to what a good wack is must be used of course. I would personally limit it to a good wack with the palm of my hand or tapping the camera with the handle of something like a screw driver. Like Don mentioned, the filter is an electromechanical unit. The electro part is 2 small electromagnets and the mechanical part is the movable tray with the filter that's spring loaded in such a way that it only has 2 stable positions, much like an on/off toggle switch only has 2 positions, either on or off. It takes very little force to cause the filter tray to switch positions which is done by pulsing one of the electromagnets on for a few millisec's to insert the filter and the other electromagnet to remove it. It also doesn't take much, like a spec of dirt, to jam things up and prevent the tray from switching positions and the idea behind all of the fixes mentioned is to help the filter switch positions and hopefully dislodge whatever is jamming things up. Besides tapping the filter, turning it on & off a few times sometimes types, but using a powerful magnet may do more harm than good as, like I said, it takes very little force to operate the filter and one could possibly magnetize some of the filter components enough to make it unusable.
I don't know if different filters are used for cameras with different operating voltages are if the same filter is used in all cases, but the filters on some of my cameras have a much louder click when operated than others and this leads me to suspect that the same filter is used regardless of the opperating voltage. If so, this may be part of the problem as I tested some filters purchased on ebay to determine what voltage they may have been designed for and found that they would work with anything greater than about 2 volts, however they could barely be heard when operated with 2 to 3.3V and it would take very little extra friction to prevent them from working. However, with 5V a distinctive click could be heard and operation was much more positive. At higher voltages the click was even louder of course and the limiting factor as to the maximum safe operating voltage is basically the duration of the operating pulse (I tested up to 24V, but pulses longer than a few few msec would likely overheat the coils.)
Barry
