Sunday, August 28, 2016

D855 GPS Fix (and possibly others)

There are some posts suggesting some hardware mods including foil e.t.c. not being to fond of this kind of tinkering I decided to read into the service manual (found on several different places, so not going to link it again) and came to the conclusion they were not targeting the correct location.
The following procedure is fairly simple (the g3 is actually fairly easy to work on), but requires bending two sensitive switches (other than that it does not even require removal of the motherboard).

WARNING: I am NOT responsible for ANY damage, problems or anything else you do to your phone, please ask someone to help you if you are uncertain or lacking experience!

Symptoms:
  • Long time to lock
  • Lock is intermittent (random signal loss)
  • No lock in crowded areas
  • Random location jumps
  • Inaccurate positioning

Fix:
Given that a GPS lock was possible and the problems occurred on multiple roms a hardware issue was the biggest suspect. For some time I held of opening the phone because previous phone's had proven quite difficult to disassemble and warranty still hadn't run out. Turns out it is nice and easy to open and look inside the g3:good:
Reading the D855 service manual on page 139 there is a section called "Checking GPS RF Signal path" (if you do not have a D855 please consult the correct manual, there could be differences between models), which points to a location on the top left side of the motherboard with some spring contacts. Given that these contacts are small my best guess was they were bent and would not connect properly anymore.
  1. Get a small screw driver which snugly fits the screws beneath the cover (as a general tool tip always ensure the screwdriver (or bit) is the correct size)
  2. Get a bowl/tray (or similar) to retain any removed items (this helps against missing screws/other small objects)
  3. Power down the phone and remove the cover and battery
  4. Remove all visible screws, take note of the one shorter screw by the camera (all other screws are the same length)
  5. Open up the back plate
  6. Bent the two connectors (see image below) slightly upwards away from the motherboard (DO NOT overdo this, breaking them would result in bigger issues, metal fatigue is easily triggered)
  7. Reapply the back plate (should click into place quite easily)
  8. Reapply the screws
  9. Reinsert the battery
  10. Add the cover (the cover contains the antenna)
  11. Boot the phone
  12. Test your GPS outside

D855 GPS connectors


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