Interested in everything electronic, doing micro repairs

Squirrel61 · 10-10-2022, 02:55 AM

Hello all,

I've got a Kobo Clara HD here which has weird hanging issues. When booting the ereader, everything is looking fine. But after a short while, the ereader becomes unresponsive and the software hangs. It looks like some hardware watchdog is kicking in, because after a few minutes of inactivity and unresponsiveness, the ereader reboots itself and everything starts again. The only way out of this loop is to keep the power button pressed until the ereader shuts off. And when I turn it on again, everything starts again.

Now the strange thing is this. Suspecting a firmware problem, I've inserted an SD-card from a known good working Clara HD and it shows the same problems. The SD-card from this Clara HD works fine in the other one. So I got myself a replacement motherboard from a Clara HD with a broken screen and it shows the same behaviour of hanging after some time. I've done a few more swaps of things and the only conclusion I can come at is that it must have something to do with the display assembly.

The display itself is fine, it doesn't have cracks or pixel faults, it's just as perfect as a display can be on a used device.

Does anybody have any idea what can be the case here? Is it possible to solve? Or should I just forget about ever using this display assembly again and use the other parts for repairs?

JSWolf · 10-13-2022, 03:55 PM

If you are not running the 4.34 firmware, I suggest you give it a try.

Squirrel61 · 10-13-2022, 04:19 PM

In the mean time, I have done some more research. When I disconnect the backlight and the touchscreen connectors, the reader still hangs after a few seconds. It even can't finish a firmware update or a recovery. But when I disconnect the display connector and let it run blind for a few minutes, it finishes everything I throw at it. That is visible when I connect the display, but a few seconds later, the reader hangs again.

So for some reason, it's the display which locks the reader. The strange thing is, as long as the reader is still running, the display is fine. It doesn't show graphical errors or glitches of any kind.

It's also not related to the firmware.

10-10-2022, 02:55 AM	#1
Squirrel61 Junior Member Posts: 3 Karma: 10 Join Date: Oct 2022 Location: The Netherlands Device: Kobo Clara HD	Interested in everything electronic, doing micro repairs Hello all, I've got a Kobo Clara HD here which has weird hanging issues. When booting the ereader, everything is looking fine. But after a short while, the ereader becomes unresponsive and the software hangs. It looks like some hardware watchdog is kicking in, because after a few minutes of inactivity and unresponsiveness, the ereader reboots itself and everything starts again. The only way out of this loop is to keep the power button pressed until the ereader shuts off. And when I turn it on again, everything starts again. Now the strange thing is this. Suspecting a firmware problem, I've inserted an SD-card from a known good working Clara HD and it shows the same problems. The SD-card from this Clara HD works fine in the other one. So I got myself a replacement motherboard from a Clara HD with a broken screen and it shows the same behaviour of hanging after some time. I've done a few more swaps of things and the only conclusion I can come at is that it must have something to do with the display assembly. The display itself is fine, it doesn't have cracks or pixel faults, it's just as perfect as a display can be on a used device. Does anybody have any idea what can be the case here? Is it possible to solve? Or should I just forget about ever using this display assembly again and use the other parts for repairs?

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10-13-2022, 03:55 PM	#2
JSWolf Resident Curmudgeon Posts: 79,778 Karma: 145864619 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	If you are not running the 4.34 firmware, I suggest you give it a try.

10-13-2022, 04:19 PM	#3
Squirrel61 Junior Member Posts: 3 Karma: 10 Join Date: Oct 2022 Location: The Netherlands Device: Kobo Clara HD	In the mean time, I have done some more research. When I disconnect the backlight and the touchscreen connectors, the reader still hangs after a few seconds. It even can't finish a firmware update or a recovery. But when I disconnect the display connector and let it run blind for a few minutes, it finishes everything I throw at it. That is visible when I connect the display, but a few seconds later, the reader hangs again. So for some reason, it's the display which locks the reader. The strange thing is, as long as the reader is still running, the display is fine. It doesn't show graphical errors or glitches of any kind. It's also not related to the firmware.

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