I'm still not convinced its the SR or tilt sensor on the K200D
A tilt sensor can be a very simple electrical device like a mercury switch. It doesn't have to be large and therefore heavy enough to
thunk. Even my old P&S Canon A75 had a tilt sensor, and it didn't
thunk.
The SR should by definition not
thunk. Its a bunch of electromagnets that can move the sensor around. Class A's description of the sound and SpongeFingers comment support this.
Its really a matter of elimination.
With my K200D I took off my lense (18-55) and put on the caps (keep that nasty dust out
), removed the batteries and rotated the camera from horizontal to vertical (ie just the body). Couldn't really hear a sound - there was a faint sound, but it turned out to be strap hitting the body.
Added the batteries and tried again....there was very faint thunk turning anti-clockwise, and louder if turned clockwise.
Added the lens instead (batteries out) - now the thunk (slightly louder than the batteries) was there, but in both directions.
So there you go - at least in my case it the 18-55mm AL II lens - there appears to be some slap from the lens that makes the bulk of the noise.
Try it out with your camera as well and see what you get.
Cheers