Lit or flashing LEDs can provide information about the status of individual components and system startup processes. The messages displayed on the monitor screen during the initial phase of system startup also have diagnostic value.
If there are no external signals it is Phone Number List worth considering the possibility of damage to the monitor itself or the cable connecting it to the central unit. Testing the monitor's operation using another computer may help eliminate this factor.
If the above steps do not resolve the issue there may be a more complex hardware fault that requires the intervention of a service professional. the motherboard processor or hard drive that are more difficult for the average user to diagnose and repair on their own. Alarm from inside the case.