Lenovo YT3-850F softbrick help - Android Q&A, Help & Troubleshooting

Hi All,
My son brought his Tablet to me yesterday and told me "It's not working". I looked at it and it was stuck on the Lenovo screen. I booted into recovery but it looks like its messed up here.
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image of issue -> ibb.co/1zCLyYr
After some probing my son tried to unlock it and load a rom, then restore stock rom and it was the last that caused the issue.
Now generally being able to get to recovery is a good thing but in this case it looks completely messed up and nothing will mount including the SD card.
It looks like adb is no longer enabled, it is not rooted and USB debugging is no longer enabled.
So it says
E:failed to mount block devices /dev/block/mmcblk1p1
E:remount block devices /dev/block/mmcblk1
E:failed to mount /sdcard (No such file or directory)
E:failed to mount /cache
And so on.
This means I can't actually get to the SD Card with any update on it if I go to apply update from sdcard there is nothing showing in the sdcard directory
Have tried the following
- Apply from ADB (Device does not connect)
- wipe/factory reset,
- wipe cache
- reboot to bootloader
I can't get into any download mode either.
I did get it at least to make a mounting noise temporarily in Windows 10 but couldn't actually get to it or browse from there and haven't been able to repeat this.
Just wondering if there is anything I can do, or whether I should just forget it, surely there is some way to connect to it.
Cheers
Dan

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Interestingly I plugged it into my mac and first it booted to a charging screen which hadn't happened last night.
Also if I leave it plugged into my mac for a little while Android file transfer eventually pops up and tries to connect but then says "Could not connect" but there is some life there at least.
A little more probing and I plug it into my Ubuntu rig and it starts to be recognized as Android but then get "Cant load MTP Device" if I try to browse it.
Looking into dmesg gives me
idProduct=78e8 (This is a Qualcomm powered device)
It then tries to mount it all but ends up mounting it as a Lenovo CD-ROM.
I can't seem to probe it past that, thinking its a futile effort but hoping for a miracle

---

Further update got it to the point where if I go to "apply update from ADB" the device is recognized and I try sideload but it just fails out on xfer 0.0

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Silvertails said:
Further update got it to the point where if I go to "apply update from ADB" the device is recognized and I try sideload but it just fails out on xfer 0.0
Click to expand...
Click to collapse
You CAN NOT sideload an official ROM / OTA update with a modified device. You must have stock recovery and be non-rooted or it will fail every single time.

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jwoegerbauer said:
You CAN NOT sideload an official ROM / OTA update with a modified device. You must have stock recovery and be non-rooted or it will fail every single time.
Click to expand...
Click to collapse
I cant do any kind of stock recovery, sideload is the closest I can get to anything, I think he must have put a different rom in there that has stuffed it up.
Is there anything I can do any steps I can take?
Windows won't recognise it so the QPST/QFIL method won't work
any steps or help would be appreaciated I have trawled every thread I can find here an across the internet

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@Silvertails
ADB Sideload is a special mode that internally makes use of / runs Android's recovery binary ( AKA Stock Recovery ).
You test whether this mode is ready or not by simply running on PC the commands
Code:
adb devices
adb reboot recovery
If successful then you in Recovery select option "adb sideload" and on PC run
Code:
adb sideload <FILE-NAME.ZIP>

---

There's a very good thread on XDA here that deals with this model and recovering from bricks.
https://forum.xda-developers.com/thinkpad-tablet/general

---

Finally got this to work.
Ordered a cable that could get me into deep download mode as jumping the pins on the mobo was not working, the cable didnt get me into download mode, but what i discovered was that if I uninstall it being recognized as a CD ROM and messing about a bit I eventually got it to recognize as an Android Bootlader Interface using the lenovo drivers. I managed to use fastboot even though the device wasn't properly recognized to install TWRP. I got a success message and managed to reboot into TWRP recovery. The device then mounted as Lenovo but a different one, but at least it was mounting.
I still couldn't copy anything over to it, so I put the OTA default ROM on an SDCard and managed to get it to install from there and update to latest versions, and now its all working again.