Power Supply

My computer suddenly cut off after being on about an hour. I suspected the power supply and so bought a new one. The machine still does nothing when I turn it on.
I tried running both power supplies directly on the bench. Both times I plugged it in, turned it on and the fan did not come on. I didn't take voltages across the connectors, becasue I assume no fan means dead power supply or at least it is not turning on.
Should I be able to simply test the power supply disconnected from the computer by merely plugging the AC voltage and flipping the switch. I thought yes, but since neither supply worked, would like an answer from someone who knows?
Thanks.

1. RE: Power Supply
lbyard Feb-17-01 02:31 PM
In response to message 0

The fan on a power supply should spin on the bench when power is applied if it is an AT power supply. If it is an ATX power supply, as most power supplies are now, the PS-ON pin on the motherboard connector must grounded to turn on the power supply. Also, many ATX power supplies now have a power switch on the back of the supply, which must also be turned on. See the bottom of our power supply FAQs at http://duxcw.com/faq/ps/ps.htm for details. Short the pins at your own risk. If you open a power supply be aware that there are dangerous voltages inside when the power is on. A power supply can still zap you, even if the power cord is pulled, if you reach inside before everything has decayed. If you open the power supply, do so at your own risk. Also, if you open it you will probably void any warrantee. Most of them have stickers on will break if the supply is opened.
The real cause of your problem may be heat related. Check to see if the CPU fan is spinning. The CMOS Setup on many motherboards will indicate the CPU fan speed if the CPU fan is the three pin type, which plugs into the motherboard. If you carefully remove the CPU fan from the heat sink you will usually see it’s manufacturer and part number. You may then be able to go to the manufacturer’s site and obtain the specifications for the fan. Look for telltale gray dust on the motherboard. It indicates a fan bearing failure. Be sure to carefully clean all of it off the motherboard. The heat sink should be properly seated over the CPU. Heat sink grease should be used for all recent CPUs. Larry

2. RE: Power Supply
gap825 Feb-17-01 05:28 PM
In response to message 1

Larry:
Thanks for your helpful suggestions.
A friend came by and actually fixed my problem! You probably know this but after trying a whole host of things, in desperation he pulled the power supply plug into the mobo and basically rocked it back and forth to break off the surface corrosion.
Voila! It worked.
Thanks again,
Glen