Assuming you do not have a broken cable and your satellite dish is aligned correctly, you can check your satellite LNB by checking the change in the values of the signal strength and quality on your TV when you put your hand over the LNB. If the values change, then your LNB is working. However, if the values remain constant when you hover your hand then you can be having either a faulty LNB or a misaligned satellite dish. But, if you have the tools, the best way is to use a satellite finder machine to check whether the LNB is working or faulty.