I picked up a 1981 model sync 300...it was welding great for about 15 minutes...then it kicked the breaker it was a 30 breaker..i know this is not ideal but its what i had at the time..so yeah it kicked the breaker and now it wont weld on ac...dc it welds fine i have full range and pedal and hf start works fine....switch it to ac and when i hit the pedal all i get is a hf current to the work piece that actual weld current never initializes...and the voltage meter reads nothing..i tried replacing the boards and that didnt fix it..thanks for any advice..oh yeah and i checked the switches at the knobs and everything is ok there