i will be getting my z1 this weekend and i would just like to ask for tips on checking the unit for the most common defects so that i can replace it on the spot. i've already read about the yellow tint defects, how can i quickly check it if the unit have it? i also read about old screen panels being used and how would i know if old panel is used on the unit? i would really appreciate for more tips on checking the unit so that i could save time for going to the store again for replacements.