Dead hudl 2 tries to boot but fails

[Guest dazmatic]

Hi all,

I've been lurking here for a little while in efforts to try and fix my fathers failed Hudl 2.

His tablet doesn't charge, no red light, no current draw from USB and I've confirmed that the charge port is fine and that battery power is reaching the board. The board was corroded and it looks like a series of power supply chips, most notably the DA6021 has failed.

I've gotten hold of another dead Hudl 2 but this one shows more life. 

No red light but it does draw power from the USB port and it has charged the battery so I know at least the battery charging circuits are fine. Equally, I do know that the device tries to boot as the PMIC fires up and presents 3.3V and 1.8V for other circuits on the board but it only appears for about 5-10 seconds and then turns off again. 

 

Is there any kind of serial terminal on the board with access to see what the board is trying to do during this startup sequence?

[Guest dazmatic]

So, seeing as I'm not likely going to get a response here which is disappointing, I figure I might as well respond to myself and use this as a log of my ventures.

To date, what I've done is replaced the nand flash on the board with the nand flash from the definitely faulty unit and suddenly I can now charge with light and charge screen, I can get into recovery and boot as far as the hudl* screen before it reboots so at least it's doing something more than it was before.

It looks like its running up to the update below as I've tried reflashing the update over ADB to no avail.

hudl2_ota_rel.android-build.20150803.092218_to_rel.android-build.20150917.142239.zip

 

So presently, it's stuck in a bootloop with no indication of what's going wrong and my searches have come up trumps only suggesting a reset which I've done several times now.