Here is how I tackled the “recovery black screen blue led” issue on my OnePlus 5T and upgrade it to LineageOS 16.0

Jon Kwok, Aug. 17, 2019

The OS of my OnePlus 5T was LineageOS 15.1(20180820) before August 12, 2019. After almost a year of using it, it was infected by a pop-up-out-of-nowhere ads virus and it was immensely annoying when I was in the flow doing what I love on my phone.

Therefore, I made up my mind to upgrade my phone's OS to LineageOS 16.0 to get rid of the virus and embrace the sweet Android Pie.

And that's when in succession I encountered the "recovery black screen blue led" issue which drove me mad and almost threw my phone to some sharpshooters to get repaired.

Followings are what I did to my phone OnePlus 5T when it's in "recovery black screen blue led" situation which to me was also a status of brickish phone :

Be prepared:

A. OnePlus 5T official anti-brick firmware (dumpling_43_H.06_171225.ops was what I found then) and the exe (MsmDownloadToolV4.0.exe, which was included in the precedent firmware compressed files) to flash the firmware into the phone.

B. Windows 10 with Qualcomm HS-USB driver to OnePlus 5T.

C. OnePlus 5T power off.

Here we go:

1. Open MsmDownloadToolV4.0.exe.
2. Connect the phone to PC with only holding the Volume Up. It's ready when the MsmDownloadToolV4.0.exe shows "Comdevice"(Com设备) and then hit the “Start”.
3. Flash OnePlus 5T official anti-brick firmware to the brickish phone via MsmDownloadToolV4.0.exe. After this, you'll get a phone like you first bought.
4. Reboot it and then update its OS to the latest version which I got was 201905 version from the OnePlus 5T official OTA push. (My phone was already "OEM unlock" when I did this. ) I think this procedure was essential so that it sent me to the right path towards LineageOS 16.0.
5. Follow the instructions from LineageOS.org for OnePlus 5T which you can find here to do the real work on your OnePlus 5T.

I backed-up all the important stuff in my phone's storage and regarded it as a brick and tried the above several times. In the end, I did it! My phone now is the latest version of LineageOS (Android 9.0 August 15, 2019) which I keep updated via OTA every day now if it has new push to me in the Settings.

I wrote these for me and those who had the similar situation for future reference.

Aug.17, 2019