Improving the brightness of old Tvs

My mom has an old tv, believe its an RCA, made around 1986, and i just uncovered it. I've been using it with a couple friends in this old shed in my friends back yard and it works fine. The only problem is the brightness. We cant watch any movie that has dark parts, which sorta takes away the whole point. Its difficult to make out faces, scenery, etc. Also looks cartoony at times. Would there be anyway that i, a 16 year old with little knowledge of electronics or the inner workings of old tvs could improve this scenario? I am willing to learn. I assume there was a time when the TV was able to handle darkness. Do i just need to replace a tube or a bulb of somesort? Or is the TV garbage? I can get more specific specs if needed, just dont feel like running over atm, especially if nothing can be done to improve it.

Thanks, sorry if this is a stupid question.