Polar M400 Watch micro-USB connector Replacement

Insert a standard paper clip into the holes on both sides of the watch that connect the watch's face with the wrist strap.

Apply an upward pressure to the holes until the locking pins release.

Use precision tweezers to remove the pins that connect the face with the strap.

Once the pins are released, the old wrist strap should snap off.

Use the T5 head on the iFixit screwdriver to unscrew the four screws on the back of the watch’s face.

Gently remove the backing from the watch.

Use tweezers to gently pry the golden sensor away from the battery.

Remove battery using the plastic opening tools.

Detach the screen from the screen protector using a PH000 screwdriver.

Make sure that the charging port remains accessible, as it can easily become detached during the replacement.

Follow the screen replacement tutorial to dismantle the watch.

Carefully lift the screen from the board.

Disconnect the USB's flex PCB from the main board. Save the red rubber seal of the USB connector for later.

Place the new USB connector on a flat surface with its pins pointing upwards.

Place the PCB on top on the pins, the exposed copper traces on the flex PCB facing the flat surface.

Using an iron, solder the PCB by heating all the pads at the same time (as much as possible) and apply pressure so that the pins of the USB connector come through.

Connect the flex PCB back to the main board.

Reassemble the watch stopping before screwing the lid back.

Add hot glue to the base of the USB connector filling the watch case's cavity. Be careful not to put hot glue inside the connector.

While the glue is still hot, put the red rubber seal back on top.

Screw the lid back.