The problem was discovered at about 5:30 a.m. when service was scheduled to begin, SFMTA spokesman Judson True said.
Regular cable car service on all lines was disrupted because of the electrical problem related to the Mason and Hyde lines.
Service was restored on the California line earlier this morning, but it took until about 8:30 a.m. today for the cars to run again on the Powell-Mason and Powell-Hyde lines.
