Put in battery, mount on camera, on it, take some shots. Zoom your lens in out, the flash zoom should zoom with it also. Press, check all buttons working. Normally the zoom lock, stuck pin happens after some usage. The flash works well and the problem can just happen one fine day. Guess just luck:bsmilie:. Underexpose?:dunno: user not familiar?
Got my first set as a gift with a 4 seconds startup and google abit to discover that it should not be this way.
Went down to the shop and exchange for another set. Tested with camera and everything is fine from startup time to zoom to wireless. Went home happily and who know days after, i needed the flash to shoot a small event and problem arises when i was preparing the night before. Slow startup and a stuck zoom.
Almost wanted to DIY to rectify the stuck zoom as i needed the flash the next day but decided against it since it is a brand new set. Ended up shooting with higher ISO with available lights.
I guess you can only test the flash to a certain extend to ensure functionality but do check on it days before your actual shoot to ensure it is working.
As for underexposure with 540, it is known to underexpose using P-TTL to ensure no detail is lose especially the highlights. Dial in a +1/3 on both your camera (K10D as far as i know) and 540 and you should see a better result instead. Test try at home to adjust accordingly.