There have been several Canon digital cameras for sale for parts on E-bay.  In the description of the item for sale, mention is made of a black display while trying to get a picture.

If that is why you are selling a Canon camera, or if you have purchased a non working camera for parts, you might want to check out the canon web site and search for "Service Notice: CCD Image Sensor Advisory (Updated 10/31/2006)"  CANON IS FIXING CAMERAS WITH A CERTAIN DEFECT FREE OF CHARGE.  THEY EVEN PAY THE SHIPPING.  ONLY CERTAIN MODELS ARE COVERED, AND JUST A SPECIFIC POBLEM.  I think that there are some video cameras covered too.

My camera, an A70 Power Shot by Canon, had a black display when trying to take a picture.  I know the display worked because I could review pictures already on the memory card and the settings were displayed.  However when trying to get a shot, the display was black and the camera didnt take pictures.  I called the number listed in their advisory and after a short discussion, Canon e-mailed shipping labels.  After I sent my camera in, it was less than 2 weeks before I got my same camera back with everything working well.  Very good customer service, and free for this problem. 

It is worth looking on line to see if what you have or what you bought is covered by the Advisory, and making a call to see if Canon agrees.

Jerel