This is a continuation of the thread titled
Kobo Aura H2O frozen and unresponsive e-reader, which needs a more technical investigation than seen in the main forum.
Just to summarise:
The problem emerged when deleting an article from Pocket and returning to main article list.
Screen refresh typically goes all white, all black then the new page data is displayed.
This time the screen froze as it was turning black and remains there with most of the new image in inverse video (white on black) and a few lines of the article still showing around one inch from the top edge, just below the text "ARTICLES FROM POCKET".
The is no visible evidence of damage to the screen or substrate and the frontlight still functions.
The device is unresponsive except for being able to power off (long press) and power back on.
When powered back on, the switch light comes on constantly for a few seconds, then flashes once a second or so for around ten seconds. The front light illuminates and then nothing.
The device is quite old, dating back to 2013/14, was obtained as a hand me down and has been used on a daily basis since birth. As far as I know it has never suffered any traumatic falls or drops, just the occasional firmware 'upgrade'.
After seeking advice on the MobileRead forum (
https://www.mobileread.com/forums/sh...d.php?t=322950), it was suggested that it may be due to a failing or corrupt SD card. I requested a SD card image and awaited the arrival of some new 16GB microSD cards onto which to put it.
Accessing the SD card requires the opening of the device. Since it is ostensibly waterproof, this is no mean feat and destroy the water-tightness of the casing. Removing the front bezel is tricky and requires a lot of care not to damage either it or the components inside. The gloop use to seal and stick down the bezel was cleaned away using Zippo lighter fluid. In my case the frontilight lightguide (the dark, translucent bezel underneath the front bezel) remained attached to the screen, unlike in many of the teardowns where is becomes magically detached without effort or explanation (looking at you iFixit/Instructables).
Four screws at the corners of the main screen/board assembly can now be removed ant the whole thing tipped out of the rear casing to reveal the main board and gain access to the SD card.
While waiting for parts as noted above, the following were tried:
i) endless messing with the power button;
ii) attempts to do a factory reset by holding down the power button and tapping the touch screen at the bottom corners;
ii) disconnecting the battery and reconnecting it to see if it unlocked any locked up BIOS/firmware chip;
iv) reseating the flat flex cables for the screen and frontlight connector.
None of these were successful.
With a multimeter, I confirmed that the battery voltage was good (4.1V) and found several power rails were present - 1.1V, 3V and 12V (at the fronlight connector).
So the board seems to be alive at least and producing the correct voltages for the main chip/RAM, the other chips and the frontlight illumination.
So the new cards arrived and the SD card image dd'd on ti it as per the instructions on the MR forum, the data partition was resized to fill the available space and it was inserted into the device.
Sadly, there was no change - the problem was not the SD card.