how to test a power supply with a multi meter -

over a quater of all computer problems. is power supply related. so it is good to know how to test your own power supply. sometimes the power supply reboots computer constantly, or it wont work at all.

first you will need to get a multi meter. there are many different brands of multi meters so I wont be able to give you exact details how to use it. so be sure and read your multi meter mannual. so you know exactly how to use it. so you do not cause damage to it.

the power supply's purpose is to take 110. and turn it into 12 volt, 5 volt and 3.3 volt direct current. the 12 is for devices and the 5 and 3.3 volt is used on the main mother board.

first check the back of the power supply and make sure the switch is turned to 115 the switch right under where you plug the cord into the back of your tower. make sure its unplugged as you switch that over if it is wrong.

now plug it in and try to turn it on. if the fan spin's then the 110 is getting into the powersupply. if they dont then maybe the cord or plug is damaged. or the fan is bad and needs replaced.

and if it dont spin plug another appliance into where you plug your computer into make sure it is getting power. or you can use your multi meter. turn it to AC power and crank it up to 115 and put the black end in the left and the red in the right of the plug. and you should get a reading on your multi meter. if not then your not getting power to your receptical.

now turn your multi meter to connectivity test. and put the black end on one end of the cord and the red on the other end. do both sides to make sure that the power cord that you plug your computer in with is good. you should get a passed on both.

ok there are two types of power supplys. the AT and the ATX. the ATX is one cable that plugs into the motherboard and the AT is two cords labeled P8 and P9. make sure your computer is unplugged from wall. now unhook the cable/s from the mother board.

here is a picture of the atx power supply plug. the clip is in between the 15 and 16 pin's. so you will be able to easily figure out where each one is located on the plug.

ok anytime the power supply is plugged in. pin 9 on the plug should always have 5 volts running to it at all times. thats a good start to checking the power supply. it does not matter if the computer is on or off it should read 5 volts.

ok now make sure all the wires look like they are in the plug good. no cuts in the wires etc. inspect them fairy good. the ATX cord has to be on the mother board in order to test it. but the AT does not. so go ahead and plug in your ATX cord. unless its a AT cord then you dont need to plug it in. go ahead and power the system up now.

ok first check the 12 volt. all the 12 volts are yellow wires. so change the multi meter to test current 15volt. now put the red tester onto a yellow wire and put the black one onto a black wire and it should read 12volt. do that for every yellow wire on there. and they all should read 12 volt. make sure you put it from the top into the plug where you see the metal at. there is bare metal there you will see it.

the 12volt's should read from 11 to 13 volts. if its 9 to 11 then the power supply needs to be replaced if left into the system you can cause the motherboard damage. so replace it asap. if its under 9volts then your computer shouldent boot at all.

now check the 3.3 volts and the 5 volts. it is very important to check the power supply because when they go they sometimes take the motherboard with it. the power supply is not something to play with. it can get violent.