There are several reasons why your computer turns but your display does not. Your monitor is simply dead. Your monitor’s power cable is not properly connected. Your GPU is not properly seated in your motherboard. Your HDMI, or DVI, or display port cable needs to be replaced. Your power supply might not be supplying enough power. Your BIOS settings may have changed and need to be set properly.
If your monitor or GPU are still under warranty then you should use that warranty to get the manufacturer of your monitor or GPU to repair your device or send you a new one.
Your monitor died.
If you suspect your monitor has died then go ahead and plug in a spare monitor from any other computer in your home. If the spare monitor does not turn on then you know you need to purchase a new monitor.
Monitor power cable is not properly seated.
Check to see if your monitor’s power cable is properly connected. Remember that your monitor’s power cable connects directly to the back of your monitor and to an outlet. Both sides need to be properly connected.
Bad HDMI, DVI, or Display port cable.
HDMI, DVI and Displayport cables usually do not go bad but in your case there is a chance your display cable has gone bad.
Below I have posted below images of what a HDMI, DVI and Displayport cables look like.
If you have any other computers in your home with the same display cable you are using then use that cable to see if that is the problem. If you do not have any spare display cables then you would need to purchase one.
Check your power strip and outlet.
If your monitor is connected to a power strip or outlet try connecting another device to that power strip or outlet to see if they are working properly. If they are working properly then we know the power strip or outlet are not at fault. Now if your power strip is not working then you will have to purchase a new one. If your outlet is not working then you will have to contact an electrician to repair your outlet.
Change BIOS settings
It is possible that your BIOS settings have changed to use your onboard graphics chip. This means that you’ll have to connect your display cable to your motherboard. Modern motherboards have DVI and HDMI connections. Modern GPUs also have DVI and HDMI connections. If your monitor turns on when you connect it to your motherboard then we know your monitor is not dead.
Go ahead and restart your computer. As your computer is restarting you will need to press one of the following keys repeatedly to enter your BIOS. F1, F2, F10, F12, or DELETE. You may have to repeat this process multiple times until you get it right.
Once you are in your BIOS you will see that it is a simple looking page. The BIOS is controlled by using the arrow keys on your keyboard and the enter key on your keyboard. In your BIOS you want to select the option that reads along the lines of chipset configuration or chipset. If you do not see these options in your BIOS then you need to use your smartphone to download a copy of your motherboards manual. I will post links below of major motherboard manufacturer websites so you can locate the manual to your motherboard. For those who are able to find the option that reads chipset configuration or chipset you can go ahead and select that option. This will lead to another page where you will be able to disable onboard graphics. Once you have disable onboard graphics make sure you save this change by heading to the exit tab. Once you are at the exit tab you will be given the option to exit the BIOS and save your changes. Once you do this you can restart your computer and plug your monitor’s display cable to your GPU.
List of motherboard manufacturers.
Click the name of the motherboard manufacturer website you wish to visit. If your motherboard manufacturer is not listed below then you can simply google the name of your motherboard manufacturer along with the word motherboard. Or you can Google the name of your motherboard along with the word manual and a link to your motherboards manual should be listed on Google’s search results.
Troubleshoot your GPU
Troubleshooting your GPU on your own is easy. The first thing to check are the fans. If the fans are spinning then your GPU is receiving power. If the fans are not spinning then the GPU might not be getting power or is dead. If you purchased your computer as a pre-built computer then the power supply your computer came with might be a cheap power supply. In this case you will want to purchase a new power supply. A 500 watt power supply will be sufficient for most pre-built computers. If your GPU fans don’t spin then your GPU might be dead but before you throw your GPU there are still some other troubleshooting methods to try out. You can swap out your GPU for another GPU. If the new GPU fixes your problem then you’ll know your GPU is at fault but still don’t throw out your GPU. The last troubleshoot method for your GPU would be taking it to a repair shop that offers micro soldering. Micro soldering is like soldering but with the help of a microscope to see all the tiny chips on your GPU and any other electronic device. A micro soldering repair shop should be able to troubleshoot any power problems in depth. They can also check to see if the HDMI, DVI, or Display port are broken and replace it.