Samsung Galaxy A12 display replacement

Ask the owner to back up the phone and switch it off completely. If the battery is more than about 25% charged, let it run down a little first. Remove the SIM tray and any memory card.

Before you pull the back cover off, find out whether the fingerprint sensor is on the back cover or on the side of the phone. If it is on the back cover, it is joined to the mainboard by a thin cable, so you will only lift the cover a few millimetres at first and disconnect the cable before opening it fully.

Warm the back evenly with a heat pad for two to three minutes until the adhesive softens. Keep the heat away from the camera area. The cover should be warm, not hot.

Press a suction cup on the back, pull to make a small gap and slide a thin pick in. Work slowly around the edges to cut the adhesive, leaving picks in place so it cannot re-stick. Stay clear of the area around the buttons. Do not pry hard at one point: back covers crack or bend.

Lift the cover slightly and check for any cable to the back cover before you open it fully. If there is one, disconnect it first. Then remove the small screws holding the plastic inner cover over the mainboard and lift it off. Keep a screw map: the screws vary in length.

Find the battery connector on the mainboard and lift it straight up with a plastic spudger. Fold a small piece of tape over the socket so it cannot spring back.

Replacement screens for this phone are usually supplied either with the frame or without it. Check the product page. A screen with a frame means you move all the parts across to the new frame. A screen without a frame means separating the old display from its frame with heat, which is risky and often breaks the old screen.

Photograph the inside of the phone. Then disconnect the display cable and every other flex cable that crosses the mainboard, including the antenna cables, the side-key cable and the charging board cable. Lift each connector straight up with a spudger.

Remove the screws and lift out the mainboard assembly. Then take out the parts you need to transfer: the battery (see the battery guide for how to release it), loudspeaker, vibration motor, charging board, antennas and camera trims. Keep small parts in a tray in the order you removed them.

Move each part to the same position on the new frame. Re-use the foam pads and gaskets, or fit new ones if they have torn. Press adhesive-backed parts down firmly. Check that no flex cable is under a part it should sit beside.

Refit the mainboard and its screws. Connect the display cable first, then each remaining flex cable, pressing each connector down gently until it clicks. Do not connect the battery until everything else is in place.

Connect the battery and power the phone on with the back still off. Check: touch across the whole screen including the corners, brightness and colours, dead pixels, the earpiece and loudspeaker during a call, the microphone, both cameras, the fingerprint sensor, volume and power buttons, vibration, the SIM, Wi-Fi and Bluetooth, and charging. If something fails, power off, disconnect the battery and re-check the cables.

Power the phone off, then refit the plastic inner cover and its screws, putting each screw back in its original place.

Clean old adhesive from the back cover and the frame with isopropyl alcohol. Fit new adhesive if you have it. Connect the fingerprint cable if the back cover has one. Press the cover on all around the edges and hold it under light pressure for several minutes.

A non-original screen may differ slightly in brightness and colour from the original. Water resistance cannot be guaranteed after any repair.