Most, if not all, digital cameras have some sort of plastic cover on top of the LCD. The plastic cover protects and seals the LCD from damage. If the LCD cover gets hit hard enough it cracks. If your LCD underneath looks like someone spilled ink on it, then you’re out of luck, the LCD will need to be replaced as well.
Are the pictures from your Canon Rebel DSLR coming out with the lower half of the frame black? When you take off the lens and push the main mirror up, does the small mirror below the main mirror not lift up completely? If so, your sub-mirror pin is broken and causing the darkness. There is a pin that functions as a hinge for the sub-mirror. When it breaks the mirror does not fully fold up into the main mirror and thus blocks some light to the CCD sensor. You can manually fold the sub-mirror into the main mirror, which will fix the problem at the cost of your autofocus functionality.
In a move of remarkable engineering Canon decided to make a critical high-stress pin out of plastic. Who would have guessed that a tiny plastic pin would break after being flexed 20,000 times? The only way to really fix the issue is to install a new metal pin, which Canon eventually did.
Cross section of Rebel mirror box
I spent almost 2 hour composing a post on how to replace the CF pin module on Canon digital Rebels, but the post disappeared when I saved it. So here’s a picture of my work bench instead. I’ll probably stop being mad at wordpress next week, and will be able to finish the post then.
The Canon EF 20-35mm is a highly rated wide-angle lens that suffers from a common AF malfunction. Many users find the focus control stops working in both auto and manual mode. An excellent article by Piers Hendrie illustrates very clearly how to take apart the lens, and one possible fix for the issue.
The cause of this problem is that the USM ring motor (#4 below) is not applying enough pressure to the focus ring (5). Pressure is applied to the focus ring via a spacer (1), wave washer (2), and a felt ring(3). When you have this issue you can still hear the USM motor moving, but the focus ring does not move.
Photo credit: Piers Hendrie
As a general rule, I repair all my own out-of-warranty electronics. So when I bought, at a significant discount, a lens that had a broken plastic outer cover on it I performed the repair myself. This particular lens was made by Tamron, who happens to sell repair parts to the public.
Here’s the damaged part.