As reported just a couple of days ago, users of the Nokia Lumia 520, 525 and 526 have in many cases found their device bricked after using the Microsoft Recovery Tool to put Windows Phone 8.1 back onto their device after running Windows 10 preview.
The company has been quick to respond to the widespread reports of the issues and has now tracked down the cause. It may be no consolation to people who now own a bricked device however.
WinBeta reports Microsoft found the recovery tool was effectively being too aggressive on the low-end devices. The tool was pushing data through to the phones faster than they could handle, so some of it got corrupted along the way.
This corrupted data meant the device could not successfully boot up after the process was complete. The tool was sending 2MB blocks of data at a time and trying to write it to the phone’s storage at 8MB/second.
As it turns out, the poor 520 simply couldn’t handle this data. The memory found it was being flooded with data it didn’t have time to process, so it ended up writing corrupt data blocks to the device’s boot partition.
Microsoft wrote on its support forums: “It was discovered that some devices are having trouble accepting the recovery image data being flashed. The blocks of data were too large for some devices to handle, and the memory on the device was having trouble with the speed at which the data was being written. In short, devices were getting too much data, too quickly. This would cause the failure as the new software is corrupted.”
Microsoft has now updated the recovery tool to fix these issues. The rate of data transfer has been massively downgraded to 128KB data blocks written at 5MB/second. This means that the process will now take longer to complete but shouldn’t end up with the low-end phones being bricked.
The new version of Recovery Tool is 1.2.4. It will be automatically installed and Microsoft advises that you do not attempt to recover any phone back to Windows Phone 8.1 from Windows 10 preview until the 1.2.4 recovery tool update has been applied.
If you own a bricked Lumia 52x-series device, here is what you need to know (and have probably been anxiously waiting for). Microsoft is continuing to research ways to recover bricked devices in an attempt to help worried owners. It has found that a bricked device will end up in one of two different states: stuck on a red Nokia logo or a black screen with complete unresponsiveness.
For those phones on the red Nokia logo, it may be possible to successfully recover the device using the new Recovery Tool version. Connect the phone to a power supply, ensure that Recovery Tool is updated to 1.2.4 and attempt to flash the firmware to the phone. More details can be found on Microsoft’s support page.
If you have a black screen, Microsoft warns that the device is in a more critical recovery state. It may be possible to flash the device successfully with the new recovery tool as explained above but the company is still investigating more details about this issue.
While this is ongoing, users still cannot upgrade Lumia 520, 525 and 526 phones to Windows 10 preview. Microsoft will make the update available again once they are confident that devices can now rollback to 8.1 successfully without being bricked.
If you have a bricked phone, follow the steps above and on the Microsoft support forum to try and get it working again. Microsoft encourages all users to share whether the process completes successfully or not to aid it in its efforts to get all bricked Lumias operational again.