Touch N905 (SD-less version) hardware problem with power supply

CatRovacer · 10-19-2016, 04:42 AM

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)

CatRovacer · 11-07-2016, 03:29 AM

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?

AbPho · 11-07-2016, 07:51 AM

At this point wouldn't you just replace the eReader?

CatRovacer · 11-07-2016, 09:23 AM

Yes, at this point better just replace burned motherbord.
But for second case (replace eink display) problem for adjust VCOM & waveform - still real.

10-19-2016, 04:42 AM	#1
CatRovacer Member Posts: 18 Karma: 10 Join Date: Dec 2015 Location: Moscow Device: Kobo Glo, Touch, Aura HD	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 04:58 AM.

11-07-2016, 03:29 AM	#2
CatRovacer Member Posts: 18 Karma: 10 Join Date: Dec 2015 Location: Moscow Device: Kobo Glo, Touch, Aura HD	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 03:40 AM.

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11-07-2016, 07:51 AM	#3
AbPho Connoisseur Posts: 57 Karma: 19100 Join Date: Aug 2014 Location: SpaceStation Earth Device: AuraHD, GloHD	At this point wouldn't you just replace the eReader?

11-07-2016, 09:23 AM	#4
CatRovacer Member Posts: 18 Karma: 10 Join Date: Dec 2015 Location: Moscow Device: Kobo Glo, Touch, Aura HD	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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