Exactly what Boots said. Just don't make the mistake of sticking a big old fuse in it to fix the problem. Back when I had the controller repair company we had some moron stick a 25 amp automotive fuse in an Irritrol DoubleDial 12. A dead short in the field caused one of the output triacs to literally catch fire and burn about a 1" hole right through the board. The guy who sent it in couldn't be bothered to check the field wiring first. He insisted that the controller was bad and that's why the fuses kept blowing. He was sad when he had to replace his customers controller due to his own stupidity and a simple wiring issue out in the field.