Dim Display problems are usually caused the by 1. a faulty inverter 2. Faulty Cold Cathode Fluorescent Lamp in side the screen (typically for the old type CCFL LCD Screens) or a faulty motherboard not outputting the correct votlage, which stops your laptop screen from illuminating.
Many companies tend replace the screen if the CCFL is faulty, this option is much more expensive, where as we can replace the CCFL for a fraction of the price.
Over the last 2-3 years LED screen have been widely used. LED screen do not have CCFL Tubes nor do they need inverters to power them.
Therefore the fault lies with the motherboard, not outputting the correct voltage to the screen or the PCB on the Screen, which can be economically repaired.
Common Symptoms are:
Faint Windows Logo
Turns on and Windows Login Sound is Present but nothing on screen