No signal to monitor

Good to everyone.
The problem is the following, there is no signal to the monitor. One writes an energy-saving mode, the second just goes out. But, connecting the computer to the plasma, everything works. The monitors are working, I checked, I also checked the cable. An hdmi cable goes to the plasma, to hdmi vga monitors ,. I changed the RAM in places, cleaned it, dropped the BIOS. The result with the plasma computer works perfectly and conveniently. But the rest of the family is not comfortable when I sit with Klava and the mouse in front of the plasma. But the monitors are black. How to solve the problem?