The camera takes distorted photos
The photos the camera takes are grainy or blurry, regardless of the settings on the phone.
Dirt is on the glass lens
If you are using your phone regularly, then dirt can accumulate on the camera lens. This dirt could affect your pictures and create blurry photos. Before opening the phone, clean the outside glass of the camera lens with a microfiber cloth to remove any external dirt or oil.
The Camera lens is cracked
If you have dropped your phone, your camera could have a crack in it. If a fracture is visible on the lens or a distorted line is visible in the photos you take, you may need to replace the lens.
Dirt is inside the lens
Sometimes through regular use dust may gather between the camera lens and the camera itself. This may also happen when the phone is dropped. To access the area between the lens and camera, you will need to access the middle housing. Once the housing is removed, use a microfiber cloth to gently clean the internal side of the glass lens and the camera sensor itself.
The rear camera is bad
Due to wear and tear your camera may die and cannot be repaired. If this event occurs, your only choice is to replace the rear camera sensor.
The sound from the speaker is distorted
You have trouble listening to sounds from your phone.
The speaker contacts are dirty
The metal contacts that connect the speaker to the motherboard of the phone may have a poor connection due to dirt or a have poor connection. You will need to access the middle housing and clean the two metal contacts on the underside of the plastic casing.
The phone won't turn on
You hold the power button forever, but the phone still doesn't turn on.
The battery is dead
Batteries can die from repeated charging and discharging. If you leave the phone charging for several hours and it still won't turn on, it may be time to buy a new battery. You can buy a new battery directly from Samsung on their website. Remove the back cover of the phone to access the battery.
If you recently dropped your phone in water, or the device was subjected to liquid, the device may be dead from water damage. To check for water damage, you must first access the middle housing. On the inside of the white plastic shell you can see a small square of white with purple Xs on it. If the square is not white, but red or purple in color, your phone has sustained damage from liquid and will need to be replaced. A good picture of the square is here (the square is just below the tweezers in the picture).
The stylus won't fit back in the slot
The stylus just won't "click" into place.
The slot is clogged
If you leave your phone in your pocket/purse, or have dropped it in dirt recently, the tube may simply be clogged with dust, lint, etc. To clean the tube, blow hard or use a can of compressed air to clear out the tube. If further cleaning is required, or something is wedged in the slot, you can access the entire length of the tube by removing the middle housing.
The nubs are worn
If the stylus does go in the slot with no trouble, but fails to stay in the slot, it may be that the stylus itself has been worn down by repeated removal. Check the stylus and look for wear and tear on the plastic near the non-pointy end. It may be necessary to buy a new stylus if such wear exists.
The phone won't make calls
Calls will not connect or they fail.
The SIM card makes poor contact
If you cannot send or receive calls on your Galaxy Note 4, then you may have bad contact between the SIM card and the phone's motherboard. You should clean the SIM card's metal contacts and reseat the SIM card in its slot(link).
The SIM card is broken
If cleaning the SIM card does not work, then you may have a broken SIM card. Unfortunately, there is no fix for a broken SIM card. You will have to purchase a new SIM card and insert it into the SIM card slot.