A few blown up PSU's , PLEASE HEEELLPPP!!!!!

hey, if somone can please help me, I've blown up 2 atx2 power supplys , cant seem to understand why this happens , I use a modified pololu electronics board it only connects to the ground and the +12v rail of a power supply , and then after a week boom.... and the power supply is dead. all I can think of that could potentially cause this is the fact that i switch the power supply on and off a lot , it powers everything , including the arduino and hot end and motors from one rail .

Edited 1 time(s). Last edit at 06/22/2013 05:45AM by spodeopieter.

Switching off and on again quickly can damage it. Some PSUs use a thermistor in series with the mains to limit the inrush current. When it is cold it has a high resistance and warms up very quickly to become almost a short circuit. That gives a soft start. If you switch it off and then on again before the thermistor is cooled you don't get the soft start. It is better to wait a few seconds before switching it on again.

The high inrush can damage the switch, or possibly blow the fuse, or the rectifiers.

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Try adding fuses between your psu, heatbed, fan circuit, controller, etc..... They are cheaper than atx power supplies.