Schoolmate!

As an engineer in an upscale hotel, I was asked to repair or replace the television in a guest room. When I arrived, the couple was watching a picture one-third the size of the screen. I knew all our spare sets were in use, so I figured what the heck: I struck the side of the TV with the heel of my hand. The picture returned to full size.
"Look, honey," said the wife to her husband. "He went to the same repair school as you."