1. The graphics card of master may be with something wrong.
Check if the graphics card breaks and the alarm of master goes off. If it’s discrete graphics card, unplug it and stick in integrated card to check if there’s any signal.
Solution: Check if there’s too much dust which would case RAM short circuit. Clean it (specially the RAM slot) and check again if the pc works. Check if the RAM sticks tightly as it may be loose when moved. Loosen RAM would cause failure when booting.
2. The wire connected display may be with something wrong.
Bad micro USB-cable connecting would cause bad signal sending and black display.
Solution: Use a new micro USB-cable.
3. The display breaks.
Use another display to connect to the master and check if it works.
Solution: Repair the display or change it.
4. The power may be with something wrong.
If the display is black while the guiding light is on, use a torch to check if there’s indistinct image. If yes, change the backlight.
If the guiding light isn’t on, press the numlock or caps key. If yes, notice the sound of system starting.
Solution: Turn on display or master power.
5. The light tube may be with something wrong.
Refer to data sheet and change the light tube or ask professional man for help.