The wires could be melted together maybe the lines are shallow and the edger blade hit them . How many zones do you have ? What brand controller do you have ? Are the Valves in one location ? I can tell you many ways to repair this >
Nestor's Sprinklers
georgia
Vincent Nestor
Nestor's Sprinklers & Lighting
Alpharetta,Ga.30022
vpn1@bellsouth.net
www.NestorsLandScape.com
www.GeorgiaLighting.net