My Sonic Complete would get more and more difficult to turn on. At first it only happened once in a while, then all the time, then finally I'd have to press the button dozens of times and/or hold it in to get it to turn on. This happened over a span of several years. The problem first appeared after I had the brush about 16 months.
After finding the notes here and the video showing how to take apart an older Braun model I did the same on mine. I was surprised at how easy it was to take the tooth brush apart.
The actual power switch is a small microswitch mounted directly on the main circuit board. The external button presses on this microswitch when the user pushes the On button.
So, this wasn't a problem of the switch sliding down and needing to be pushed back up as noted in another post below; nothing had moved or shifted.
This mircoswitch sits on the circuit board and is electrically connected via 4 tiny solder joints. I suspected that there might be a break in one of the joints, causing intermittent contact. Pushing the on/off button places stress directly on the switch, which sits directly on the circuit board. If the cct board is not rigidly connected to a large, stiff surface the board can flex slightly, eventually causing one or more of the solder joints to crack and fail.
I have a small tipped soldering pencil from my days as a electronics technologist so I just resoldered all 4 joints.
Bingo, problem solved. My Sonic Complete now turns on and off each and every time I press the power button. I should have done this much earlier, instead of frustrating myself by having to press the on/off button over and over.
If you don't know how to solder and/or don't have the right tools, ask around and see if any friends could do it for you.
DW
November 2009