A motherboard with no display could be because of many reasons. for example , bad graphic card, Bios corrupted, display connector, CMOS, RAM, CPU and many more. As you said you already tried different Processor and RAM but it still fails. Please try these few steps it might work for you if you don’t have a bad graphic card chip or bad BIOS.
- Please remove CMOS battery from the motherboard, next remove RAM, next remove your Processor, Now take some tweezers and touch the positive and negative point of CMOS connector on the board (So it can change BIOS to default remove any static current from the board), next connect your Processor, then your RAM and last your CMOS battery and test it for display.
- If the above trick didn’t work for you, what you need to do is program BIOS chip (To do that you will need BIOS programmer)
- If you don’t have any Programmer you can try the link below where I explain few more steps about a laptop with no display.
- here’s the link https://howtofixlaptop.com/laptop-led-lights-on-but-no-display-no-picture/