power supply

hi guys today i went to turn on my pc. on the back of my tower bent of to switch on the power supply and when i switched it on i heard a big bang and then all the power power went off. i went outside and checked the fuses and one of the fuses was blown so im gguessing dose that mean i need a new power supply. this dosent always happen just now and then????????so dose this mean i need a new power supply????

hi Shadowjk when i switched on the power supply from the back of my tower i heard a big bang but the pc still turns on this has been happerning for a while and i dont know whats causing it. but im worried if it happerns again it might dameg my hardware. so i dont know what to do. every time this happern the fuse for the house blows not the pc. pc still runs ok. but i want to know whats causing this.

also how do i test my power supply to see if its running 100% is there a software tool to use???

only when i flick the switch on from the back then bang the power goes off then i have to go to the switchboard and fix the fuse thats blown. i repeat dis dosent always happern just now nd then and its kinda ***me off.

i aslo did an insulation test on the cord that plugs in to the power supply but i found no short circuit and the tool i used is an analog insulation tester.

It sounds like the PSU is bad to me and it should be checked out before it does damage your computer, or something worse. Though rare, anything that plugs into the wall can start fire, or kill. Here's my canned text on testing PSUs.

To properly and conclusively test a power supply unit (PSU), it must be tested under various realistic "loads" then analyzed for excessive ripple and other anomalies. This is done by a qualified technician using an oscilloscope or power analyzer - sophisticated (and expensive) electronic test equipment requiring special training to operate, and a basic knowledge of electronics theory to understand the results. Therefore, conclusively testing a power supply is done in properly equipped electronic repair facilities.

Fortunately, there are other options that are almost as good. I keep a FrozenCPU Ultimate PSU Tester in my tool bag when I am "in the field" and don't have a good spare power supply to swap in. While not a certain test, they are better than nothing. The advantage of this model is that it has an LCD readout of the voltage. With an actual voltage readout, you have a better chance of detecting a "failing" PSU, or one barely within specified ATX Form Factor Standard tolerances. Lesser models use LEDs to indicate the voltage is just within some "range". These are less informative, considerably cheaper, but still useful for detecting PSUs that have already "failed". Newegg has several testers to choose from. All these testers contain a "dummy load" to fool the PSU into thinking it is connected to a motherboard, and therefore allows the PSU to power on, if able, without being attached to a motherboard - great for testing fans, but again, it is not a true load or suitable for conclusive testing.

Swapping in a known good supply is a tried and trued method of troubleshooting, used for years even by pros. If you have access to a suitably sized, spare power supply, carefully remove the suspect supply and replace it with a known good one and see if the problem goes away.

I do not recommend using a multimeter to test power supplies. To do it properly, that is, under a realistic load, the voltages on all the pins must be measured while the PSU is attached to the motherboard and the computer powered on. This requires poking (with some considerable force) two hard and sharp, highly conductive meter probes into the main power connector, deep in the heart of the computer. One tiny slip can destroy the motherboard, and everything plugged into it. It is not worth the risk considering most multimeters, like plug-in testers, do not measure, or reveal any unwanted and potentially disruptive AC components to the DC voltages.

Note the required voltage tolerance ranges:

And remember, anything that plugs into the wall can kill. Do not open the power supply's case unless you are a qualified electronics technician. There are NO user serviceable parts inside a power supply.