First, look at the LED on the outside of the box if it is on then the supply is working and the problem is probably an open poly switch (fuse). To correct this on the 1AMP supply, disconnect the load for 15 seconds, correct any possible system shorts and then reconnect the load. On the BPS series supplies over 1AMP each output if fused and the output LED will be on if the output is working. If the LED is out disconnect the output using the associated slide switch correct the system short and then reconnect the output with slide switch. The LED should go on and the system should operate. If all of the LEDs are out use a meter to check between F1 and F2 on the power distribution board if you see system voltage here then your fire alarm has disconnected the system.Second, if the LED on the outside of the box is out check the AC input, if there is no AC voltage present you have found your problem.Third, if AC voltage is present check the AC input fuse. If the AC input fuse is good and you have checked everything else call the factory.