[Circuit Sowrd 1.3C] LCD Not Working

[pbuyle]

Hi, I'm cross-posting my issue from the Support Kite's Product
after getting no answer there (original post is several months old).

I got a Circuit Sword (1.3C) with the 320x240 screen in 2019, everything worked fine. I got several hours of fun on it.
I got a new Circuit Sword (1.3D) with two _new_ 640x480 screens (the ones with no adapter) in 2020. The idea was to make a new build and upgrade the screen of the existing one. The new build went great, everything worked right away.
Getting the new 640x480 screen to work on the 1.3C is when trouble began. I followed the guide, upgraded everything, solder the BL-BOOST pads. Since then the screen stay black (with backlights on). I tested all the screen on the new 1.3D board (which has been gifted since then) and they worked fine. After reverting everything to use the 30x240 screen, the screen still stay black (again, backlights are on). The rest of the system seems to work fine, I can even SSH into it if I configured the Wifi from the boot partition. But I can't get the screen to work. I started from scratch with an new SD, no change.

I suspect a hardware issue, and I can't rule out messing and breaking something myself since the board was working fine before. But I've no idea how to troubleshoot this further. I checked voltage everywhere I could and everything seems find. You can find more details on the issue and everything I tried in the original topic at https://www.sudomod.com/forum/viewtopic ... 51&t=10396