A colon can create a small promise: the words before it prepare the reader for what follows. Testing that relationship is more useful than adding the mark merely to make a sentence look formal.
Write a complete lead-in
Try an invented example: “The cupboard held one useful thing: a torch with working batteries.” The second part identifies the thing promised by the first. Remove either side and you can see what the connection contributes.
Now compare a looser version: “The cupboard was old: a torch with working batteries.” The relationship is harder to recover because the lead-in has not prepared that information.
Decide what kind of delivery you want
The continuation might supply an explanation, an example or a short list. Choose the form that answers the expectation you established. If you need a different thought rather than an elaboration, a full stop may give it more room.
Read the revised sentence aloud, paying attention to the anticipation before the second part. The punctuation works best when the underlying thought already has a clear relationship. It can sharpen that relationship, but cannot create a missing logical connection by itself.