Friday the 13th: The Series - Season 1 Episode 17
The Electrocutioner

An innocent man is condemned to the electric chair, but manages to survive. Embittered, the man buys the electric chair from Lewis Vendredi. A dentist, he takes a job in an orphanage and disguise it as a dentists chair. He then kills the orphans and covers up their disappearance by claiming they are runaways. The killings let him electrically charge himself into a living dynamo, so that he can go out and kill those responsible for finding him guilty at his trial. The trio must ground him before he can kill again.