Yeah the 42" is very thick bezel at the back good spotting, its taking up pretty much the entire back base.
see here its more clearer:
But the 48" which is few inches bigger totally different see here:
The mainboard and ps are all placed at the bottom half tv casing almost.
Its a bit of a curious design really, could the electronics really take up all that space?
One thing I spotted is the LG C2 42" has all 4 hdmi ports and all the ports on the side which is far better then the C2 48" which has 1 hdmi port on the back and some other ports also which is a pitta if you are wall mounting or pushing the screen back against the wall which naturally TV manufacturers don't do
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Maybe this was why they had to arrange the mainboard and p/s to take up all the space of the 42" back casing.