Boyue T62D black screen

[qwerto]

Dear friends,

I have the e-book reader Boyue T62D for almost three years. It was running for long the original firmware (I suppose version 150831) almost properly, there were only sometimes problems to wake up from sleep mode, it was necessary to plug the cable to power source. Recently I updated to the official firmware update (version 161119), I copied the file update.zip to internal SD card and rebooted, everything went correct. But after some time my T62D collapsed very strange way. When I switch it on, it boots up, the screen is without backlight showing starting boot image, that is OK. But after some time the screen freezes and the backlight goes on. And then the screen turns black with backlight on and that is all, after some time it only turns off the backlight and goes to sleep mode. But the device is running, but there is no screen response. When I connect it over USB to the PC, disks are mounted as Mass Storage and I can see my data disk. When I flash Gonyx, I even have adb. I tried flash new firmware, original ones and also Gonyx, with RKBatchTool_v1.8 (both options Upgrade and Restore), with ROMKDumperTool_v2.1, I did something like factory reset over adb, but nothing changed. I am not sure if it is the sofware or hardware problem, but if it is hardware one than I supposed not the broken display, which seems to work properly in the first stage of booting. I would be glad much if someone could help me to get my T62D back to life.