When it comes to diagnosing a faulty laptop screen, it's important to understand that rare causes are more common than you might think. While technicians may misinterpret a diagnostic test or a spare part may be faulty, these rare causes should still be taken into consideration when all common and possible problems have been ruled out. If you can't detect any indicators of where the fault is, the best option is to take the laptop to a repair center for diagnosis or take the risk of replacing the part you think is the culprit and hope that this will resolve the issue. It's important to note that if technicians spent 100% of their time diagnosing every repair job, the cost of repairing a device would be unaffordable.
Therefore, it's essential to check if the images displayed on an external monitor are correct. If they are, then the problem is likely with your laptop, not the screen. In some cases, it may be necessary to buy a completely new unit. If your laptop doesn't stay on when it's turned on, you may have a hardware problem and should take it to a repair center for diagnosis.
If you connect your laptop to an external monitor and still see a black band, then you should take it to a repair center or buy a new unit instead. The only way to know which of these three options is the problem is to take your laptop to a repair center for diagnosis or replace the screen or cable and see if this resolves the issue. Older laptops had a locking mechanism that allowed the cover to be opened from the center, however, today's laptop manufacturers focus on fashion rather than function, and offer thinner and sleeker designs, which in turn makes these devices more susceptible to accidental damage.