A blurry cathode ray tube (CRT) monitor is nothing to be worried about. Just because the screen is blurry does not mean you should begin making plans to throw it out. Most CRT monitors can be fixed by going through just a few, simple steps.
Clean your monitor with a special screen-cleaning tissue before beginning the repair. These tissues can easily be found at any office supply or computer store.
Degauss the monitor. This can be achieved by pressing the degauss button on the front of your monitor, though most modern-day monitors degauss as soon as the monitor is turned on. If you ever hear a buzzing noise when you turn on the monitor, that is the degauss circuit working. This removes any stray magnetic fields around the monitor, which in turn can distort the image onscreen. In the event that you do not have a degauss button on the front of your monitor but wish to manually activate it, cycle through the menu of your monitor; there will be an option available to degauss.
Adjust different settings for refresh rate, screen resolution and colour depth via the display properties. Do not be afraid to play around with these settings, as one setting could potentially fix your monitor and no harm with come to your computer by doing so.
Adjust the convergence controls in the on-screen display if the previous step did not fix the blurriness. If adjusting the convergence controls does not work, simply select the Factory Reset option in the OSD. This will return the monitor to the state it was in when your monitor was purchased brand new.
Ensure the video signal cable is firmly inserted into both the monitor and the computer if the previous step does not fix the problem. The cable may be relatively loose on either end, causing the monitor to become blurry. If the problem is still not resolved, test the monitor on a different computer. If the monitor is still blurry, then it is probably time to buy a new one.
Always keep your monitor clean and ensure that a firm connection between the computer and the monitor is present.
When manually degaussing a monitor, never hold the manual degauss button for more than a few seconds and always wait at least 20 minutes before manually degaussing again. Always keep magnetic media (e.g., external hard drives, flash drives, etc) away from a monitor when powering it on and most especially when degaussing. Because the act of degaussing involves removing magnetic fields around the vicinity of the monitor, it could potentially damage and erase information on your magnetic media.