Originally Posted by RandyWalters
I think the most likely cause of some devices and TV working with the voltage converter while others do not has to be because of the hertz thing. Some devices (like a shaver or DVD player or even some LCD TVs) are dual-rated for 50/60hz, while other items (like a Panasonic Plasma and my friend's Sony LCD TV) is rated only for 60hz. I don't know if the voltage converters sold in the UK are also capable of converting 50hz to the necessary 60hz, but back when i was helping my friend find one with this ability i didn't come up with any at all (i even searched all over the UK-based AV Forums). The converters seem to just convert the voltage only, but not the hertz (i don't know if that's even possible).
Randy - whether the set locks to 50Hz video sources is not related to the mains frequency, if it doesn't work it is likely to be that the HDMI inputs don't lock to a 50Hz HDMI signal. So it is a "Hertz thing" - but not the mains power supply, but instead the input stages. You are right that some power supplies don't work optimally at the wrong frequency - but because Japan runs with both 50Hz and 60Hz 110V - maybe 100V? - power you're usually fine with 230->110 step-down transformers that work at 110V 50Hz. HOWEVER you do need to make sure that you have a step-down transformer that is rated correctly for the power consumption of your equipment. In fact one thing that famously causes problems is electric clocks if they are line-frequency locked. They'll run very slow in Europe! (Which is why some have a 50/60 switch on the back)
I work in the broadcast industry in the UK, and when I've worked on shows in the US (which we usually try to shoot at 1080/50i to avoid conversion in the UK), we have to take great care to ensure that in-vision monitors are going to lock to our 50Hz sources (even though they are plugged in to US mains supplies!) I did a show in Hawaii 2 years ago (live to the UK) and we found that a Chinese no-brand LCD was fine locking to 1080/50i (i.e. UK frame rates) but Sony and Panasonic models wouldn't work at all... (You can imagine me in Walmart with my laptop outputting 1080/50i ;-) )
I posted a much fuller answer in the OPs alternative thread.
Bottom line. European HDTVs will lock to all frequencies (50 and 60Hz) as it is mandated under European licensing that both 50 and 60Hz are supported. In the US there is no requirement for 50Hz compatibility, and so many mainstream US-specific models don't support 50Hz. 50Hz input compatibility is required for connection to European set-top boxes for cable, satellite and OTA, as well as for European DVD players. Whilst you can get frame rate converters - their quality is pretty low. If you care enough about picture quality to have an HDTV, you'll want something better.
I'd recommend buying a set in Europe, secure in the knowledge that it will work (subject to mains power conversion if needed) back in the US with US set-top boxes with few problems (though it won't have an OTA / Cable ATSC tuner in it)