Micromax A85/Cherry Magnum 2x/ K Touch W700 Hard Bricked and then Unbricked!!
Some time back i mistakenly wrote wrong bootloader to my Micromax A85 through nvflash. Since then it was showing just blank screen(just backlight). I had the stock images, but couldn't restore them because the phone was not going into APX mode (the volume+ while booting wont be recognized as the bootloader was wrong). The Full battery drain trick didn't worked as the whole internal storage was re-partitioned and i used wrong Omdata, i believe this caused not to boot into low power mode.
I checked the docs for the Tegra2 dev boards and they had the seperate switch for going into APX mode, they call it recovery button. I have attached the tegra 250 doc i referred. So i knew that the pin should be there on the board and may have to open the phone to access them (void warranty/go to the service center ). When i removed the battery, saw some contacts on the board, attached the image and marked the contacts with the red circle, didn't even opened the board . saw TBW 7801 written on the board and googled it, got some chinese pdf for Ktouch w700 which is same model, attached it. If you see the manual, they have given the pin TP940 (bottom right pin) for going into AP Recovery mode:
RECOVER_MODE = 0 USB RECOVERY MODE
= 1 BOOT FROM SECONDARY DEVICE
This pin is connected to 1 so that phone always boots from internal memory. I just needed to make it 0 when switching the phone on . Did it with simple wire to connect it to TP1143 which is ground (logical 0, top left pin). This time phone didn't went to backlight and was full blank, not even the vibration at the start and saw Nvidia Corp on the lsusb .
Got into APX and then recovered to gingerbread (cherry magnum 2x) instead of stock froyo.
This should be applicable to any tegra 2 device given that they have the access to GMI_OE pin.