Answer to: My callers hear an echo, I dontI know this is a good while now but here is my 2 cents worth as i have encountered this a fair few times now. i have found that the echo goes away when battery cover is removed but reappears when pushed back on. i wanted to get to the bottom of this as it did not seem like a hardware failure. firstly (the obvious)remove any protective case and check if same issue. then for only testing temporarily!! ,try sticking a pin or covering up best you can the tiny hole for top mic which is located beside earphone jack. if you find the echo goes away then try next step below (you dont want to permanently completely block this hole as you will have poor speakerphone and video audio quality). The proper fix would be to put a thin layer of foam in between the top mic and black rectangle mount shown in image . it can be done carefully with only having to remove battery cover. a thin screwdriver in between these areas will prise and give some slight access. Best to work from left hand side of top mic incase you rip cable on...
Answer to: Overheating and battery drain after Falli can confirm replacing the camera can rectify it. even after a restore the iphone 4 was running hot (even power button felt hot!) and massive battery drain. there was a tiny chip on the front screen by power button indicating a fall. replaced the camera and now the iphone is stable. not hot and no drain "Everyday's a school day" they say
Answer to: After taking apart phone, slight pressure on the lcd causes rainbowsFrom my experience its usually the battery causing it. When you remove it with a pry tool (since the pull tab is usually useless, I always use a pry tool.) The pry tool can sometimes put a tiny lip on the battery towards the rear of the battery causing more pressure against the mid plate. I always beat it flat before inserting the battery again. Took me a while to figure this out as you wouldn't believe how small the deformation has to be to cause a pressure mark.