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Old 10-19-2016, 05:42 AM   #1
CatRovacer
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Question N905 (SD-less version) hardware problem with power supply

I have eink reader Kobo Touch N905 with the "gray" work:
- After hardware reset to the factory settings, blue LED flashing, the display sometimes shows signs of the passage of the process ("book-smiley") However, the image is very low-contrast, almost gray.
- Up to ready (user operation) state does not reach.
I have connected to the UART lines, click Reset, observe the boot process:
Code:
Enable Blue LED
MC13892 volt: 406
Setup env for booting..
No Card in Slot
Normal boot mode, using default boot env
Hit any key to stop autoboot: 0
6144 blocks read: OK
## Booting kernel from Legacy Image at 70800000 ...
Data Size: 1862612 Bytes = 1.8 MB

Starting kernel ...

Uncompressing Linux... done, booting the kernel.
mxc_epdc_fb mxc_epdc_fb: Display HW not properly initialized. Aborting update.
1+0 records in
1+0 records out
512 bytes (512B) copied, 0.004886 seconds, 102.3KB/s
cannot open /dev/null
dosfsck 3.0.6, 04 Oct 2009, FAT32, LFN
mxc_epdc_fb mxc_epdc_fb: Failed to match requested video mode
mxc_epdc_fb mxc_epdc_fb: Display HW not properly initialized. Aborting update.
/dev/mmcblk0p3: 181 files, 4870/358650 clusters
FAT: utf8 is not a recommended IO charset for FAT filesystems, filesystem will be case sensitive!
mxc_epdc_fb mxc_epdc_fb: Failed to match requested video mode
Power Good Status : 0xba
Enable Status : 0xaf
waiting for power good retry 0
.....
Bold highlighted lines repeated

On board there is single-chip power supply IC for eINK TPS65185 <- .pdf here
Compared with a worked same device noticed a significant difference in the control voltage of pads:
VNEG -15V and VPOS +15V, instead on good ereader: 0V both

Any ideas? Which defective?
(i can reflow chip, but delivery time too long)

Last edited by CatRovacer; 10-19-2016 at 05:58 AM.
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Old 11-07-2016, 04:29 AM   #2
CatRovacer
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1. This board more "downgraded"
some detail is strongly heated. define the smell, immediately turn off. I do not want to watch the outcome of "the magic smoke". I'll try to find a the thermal imager.


2.How to adjust VCON voltage for Kobo Touch N905, GLO?

I rewrited internal (system) SD card for GLO and get more gray background of display.
Image file from other same ereader (only SN changed)
I think VCON sew somewhere inside Nickel, but where?

Last edited by CatRovacer; 11-07-2016 at 04:40 AM.
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Old 11-07-2016, 08:51 AM   #3
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At this point wouldn't you just replace the eReader?
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Old 11-07-2016, 10:23 AM   #4
CatRovacer
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Yes, at this point better just replace burned motherbord.
But for second case (replace eink display) problem for adjust VCOM & waveform - still real.
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