power supply may be crowbarring. when you arrive, check power supply 1 for 120 vac input, if it has 120v and the 5, or 12 output supply is 0, then you are probably crowbarring the power supply. power supplies will crowbar when the current exceeds a certain amount, usually set by the current pot, they will not blow a fuse if designed in the circuit properly, and this can be confusing if you don't know about the crowbar effect. some power supplies have a voltage adjust, and a current adjust. If yours has a current adjust pot, then turn it up and see if that may take care of the problem. if not sure which way to turn it, monitor the output voltage and turn the pot until the voltage drops to zero, then turn pot the opposite way and recycle power that way you know which way to increase your current ..
also it could be that one of your boards is pulling excess current occasionally, but i would start with power supply.
