How to diagnose Samsung Galaxy A40 Charging Problems

These photos depict the +5V line from the charging port to the motherboard.

Heat the device to soften the adhesive.

Tools you may find of use include a playing card, suction cup, plastic tools such as picks and a spudger and isopropyl alcohol (preferably not rubbing alcohol - contains oils and perfumes).

Remove the silver Phillips screws from the device's frame.

Remove the plastic cap from the fingerprint flex cable connector and disconnect the cable.

Remove the SIM Tray.

Use a plastic tool to separate the back cover from the frame. Start from the SIM tray hole.

Disconnect the main flex cable and connect the charger.

Use a multimeter to measure the voltages at the large end pins of the FPC connector of the charging board. (See the second image)

If the reading is okay (~5V) continue with the next step, if not - change the Charging board.

Attach the main flex cable and measure the large end pins of the Main flex FPC connector - pic.3.

If the reading is okay, continue with the next step, if not - change the Main flex cable.

Remove the adhesive rubber around the main flex connector on the logic board.

Use some flux and a soldering iron to re-solder the first pin of the motherboard FPC.