The computer turns on, all fans are noisy, but the screen does not light up. What could be?

The computer turns on, all fans are noisy, but the screen does not light up. What could be?

Anything. Starting from the power supply, memory, video card, motherboard, processor and contacts. Diagnostics is required, you need to take the computer to us. This is 800 rubles. Next, we will say what is faulty and how much it costs to fix.