What should I do if the computer can't open the machine?

[alld...@gmail.com]

When the main unit is turned on, the main unit light is on, the keyboard light is off, and the display shows no signal. Then shut down, the host will not open when the second boot. To unplug the main unit, wait for about 5 minutes and then reconnect to the main unit to start the main unit. The display is showing no signal, the keyboard light is not lit. What is the reason, which hardware has a problem? Thank you
I have ruled out the memory stick, the CPU problem. The power supply fan can be turned, and the CPU fan can also be turned.
I also pulled out the discrete graphics card and replaced it with an integrated graphics card. The host is turned off, and the host cannot be turned on immediately. It takes a few minutes to turn it on again. Before the bad, when the socket was connected to the power, the host was not turned on, the host suddenly started, and the display had no signal. It is so bad.https://www.allicdata.com