I took the daughterboard out to find the hall effect sensor, and I'm reasonably certain
this is it. That puts it between the USB port and headphone jack, which is at the very bottom edge of the magnet in the screen bezel,
as seen in this picture with the main body laid over the lid with bezel removed.
Here's a photo of the magnet in its original location, and
here's another of my revised location.
The lid is designed with its own cutout for the magnet, but this cutout is not necessary and may even be the cause of the finicky sensor operation. I'm not sure whether it was the inward movement or the downward movement of the magnet that affected its operation, but I can say after testing that
the new placement of the magnet results in proper operation of the hall effect sensor. My lid is completely closed, and the PBP is sleeping as it should be.
You can see in the final photo in the top of the frame there's a foam spacer that keeps the LCD panel from rattling around in the lid assembly. The magnet happens to be the same width, and is affixed magnetically to the LCD panel, so adhesive doesn't seem to be necessary.
As mentioned in a previous post, it may be technically possible to issue a software fix for this by adjusting the input voltage RK3399 is looking for from the hall effect sensor. If you can't wait for a possible software fix, perform the hardware fix below at your own risk.
If you want to attempt this fix yourself I would advise taking your time with separating the bezel from the lid to avoid any damage. It's not difficult, but you have to be careful. The most frustrating part to remove was the plastic cover from the bottom of the assembly to expose the metal hinges.
Removal steps for display assembly:
- Remove bottom cover.
- Disconnect LCD and webcam ribbon cable from main board. Flip the small black strip on the connector upward and the ribbon cable can be easily removed. DO NOT pull the cable out without first raising the black retaining mechanism.
- Remove the small black plastic spacers on each hinge and set aside.
- Remove the three screws from each hinge on the display assembly.
- Move the hinges upward to a 90 degree angle independently from the main body. Then lift the main body to the same 90 degree angle and you should be able to separate the display assembly from the main body. Set the main body aside.
- Remove the plastic hinge cover on the display assembly. There's not really an easy way to do this, just work slowly and deliberately so as not to damage the sensitive cable inside. Start from either end and work your way inward. Use a small flathead screwdriver or similar tool to get started.
- Remove the hinges from the display assembly.
- Remove the rubber bumpers at the top corners of the display assembly to expose two screws. Remove the screws.
- Starting at the corners, separate the bezel from the lid. The clips that hold it in place are similar to those found on the hinge cover. Again, slow deliberate work will get it done. Work from the top down. Take care not to damage the cables in the bottom.
- With the bezel separated from the lid, feed the cable through the slot and set the bezel aside.
- WITHOUT removing the LCD panel completely, lift and move the panel slightly to the left, taking care not to damage the cable running underneath up to the webcam. This will give you room to remove the magnet without risking damage to the panel.
- Pry the magnet out with a small flathead or similar tool. There is some adhesive but it's not very strong.
- Move the magnet down about 1-1.5cm and put the LCD panel back in its place. The magnet should fit perfectly and adhere to the panel, so no need for adhesive.
- Reassemble using these steps in reverse order.
If this imformation is found useful, I would be happy to add it to the wiki.
