I thought the firmware could have problems, but it worked in bluetooth handsfree and then I did not understand why.
Having experience in microelectronics with my work repairs transceivers I could not resist and I opened it.
Well I managed transaction, it works fine now and the owners of this beautiful phablet who want to see what's inside you can watch the album that I uploaded in the profile.
Greetings to all. max
Pardon for the foto , update directly on post now .
1 back of K900 with 4 torx screw and his screwdriver T06x50
(turn the screws to the left and then take them off and put them in a glass so as not to lose them)
2 how to separe live parts from bottom with razor blade
(insert the blade in a very kind and gentle, making a small force to the outside of the body until they snap the little plastic teeth that hold the body of the display with the shell, there are 3 teeth on the short sides and 4 in those long)
3.1 internal of bottom
(the inner part of the shell contains the contacts for the antennas and for the metallic screen)
3.2 all in one after open
(around the block phablet, we can see the 2500ma battery, the motherboard with L-shape, a lower block with micro usb, speaker and microphone, and an upper block with cameras inside and outside, proximity sensor, LED flash and the small headset, the vibrator has a round shape)
3.3 allin1 without back
(view of the whole, is very compact and simple, and the distribution of the components makes it easy disassembly and reassembly)
4.1 remove battery
(the battery is simply attached to the body with a small layer of double-sided adhesive, easily removed by pulling the tab transparent and removing the connector with a toothpick, making a slight force to lever)
4.2 zone two camera , earpiece , vibrator and proximity sensor
(to remove the motherboard, unscrew the small black screws with a Phillips screwdriver, there are 7 screws, one is covered by a sticker type security seal around the LED flash, on the other hand to remove the upper frame of the camera there are 2 white screws, the I have not removed the bottom for comfort)
4.3 remove small motherboard
(pay attention to the layout of the connectors and remove them again using a toothpick to avoid damaging the delicate tracks of the circuit, remove the motherboard and place it in a safe place, preferably on a sheet of paper and not plastic electrostatic)
5 back display dissasembly back wiew
(after releasing the back of the display from the motherboard and the top frame I discovered that the small headset was placed upside down and the contacts did not touch on the slopes of the circuit itself, I measured with a multimeter and it was ok 31 ohms , helped by a lens I checked on the contacts of the circuit if this were the marks left from the headset but were not present, a clear reference to a wrong installation)
6 rear of earpiece with contacts and reference
(the offending piece, you can see the notch and the corresponding joint in the display, well, when I opened it was the opposite, in fact the phablet worked with Bluetooth and Handsfree)
7 reassembly and test before closed
(I reassembled everything by reversing the procedure, taking care to insert the camera frame by repositioning the headset correctly, the vibrator and by matching with a lot of patience and chassis backplane, repositioning and tightening the screws excessively , reconnecting the battery and inserting the sim I turned it on, I checked that it worked by calling the remaining credit service , then I turned it off and removed the sim to close permanently)