When your computer screen goes black randomly, you are left helpless as nothing is visible on your monitor screen. This, for most, is a reason for panic, as you may not know where to start the troubleshooting process. Like most computer monitor problems, here too, the main reason is either with the video card or the power supply to the monitor. Sometimes, your computer screen could also go black during startup even before it boots. Before you rush to a qualified technician, follow instructions given below to find out the possible cause. If you are lucky, you can solve the problem yourself at home and save some money. Reasons for the Screen to go Black Moisture The most common reason is moisture. Whenever the computer monitor is put in a humid environment, water tends to condense and collect on the insides of the monitor. Due to this, absolutely nothing is visible on the screen. A good way to solve this problem is by leaving the monitor alone for a while, so that any moisture accumulated evaporates. Defective Graphics Card Another common reason for you computer screen to go black is a defective graphic or video card. A good way to figure this out is by connecting a new monitor to the CPU, and checking if the problem still persists. If the screen stops appearing black, then the problem is something else; and if the screen does continue appearing black, then you need to repair or replace your graphics card. Defective RAM Though not very common, there is a possibility for the black screen after start up to be due to faulty RAM. Bad RAM modules can prevent the computer from booting properly, even through the basic BIOS setup. It is extremely difficult to detect this problem as you might have to install the RAM in another computer and then check. Lack of Tight Connections Loose connections are another reason why your computer screen could go black. Check both, the connection from the monitor to the main power supply, and the connection between the video card and your monitor. Ensure these connections are tight and proper before you go on checking other parts of the computer. Motherboard Short Circuit A short circuit in the computer motherboard could also cause the monitor screen to go black. This is the worst possible reason, as the only choice left with you is to replace your motherboard with a new one altogether. Even though chances are less, there is a possibility this could happen. A good way to prevent this problem would be ensuring all connections on the motherboard are proper and tight, without any loose ends. What to do When Your Computer Screen Goes Black on Startup? Check For Bleeps The first thing you must do when your screen becomes black on booting, is to hear the bleeping sound it makes. In case you hear only a single short bleep, proceed to the next step. But if you hear a long bleep or multiple bleeping sounds, it is an indications of a major problem and the best thing to do is to get your computer checked from a technically qualified person. Examine Monitor Cables Since a loose connection of monitor cables can be the cause of the problem, check the connections. The power connection as well as the video card connection should be secured and firm. Examine All Enhancement Cards The video card and all other graphic cards should be firmly fixed in their respective slots. Check all these connections on the motherboard by opening up the CPU case. Secure them if necessary. Although the video card is the one you are concerned with, any other ill-fitted graphic or sound cards can also be the reason. Examine Power Supply Connections This is the last thing you need to check. All power supply connections of the computer including the CPU, the monitor and other external devices must be tightly connected and secured. If your screen goes black even after trying out the troubleshooting instructions given above, then it is time you get your machine checked from a qualified technician. It could be a major problem and a proper, prompt repair will prevent it from aggravating further.