testing a 24 pin power supply

[peter2679]

hi,

i have this antec neopower 480 w power supply that supposedly died last november. i remember that i had used this nifty little power supply tester to test the 24 pin connector. at the time i saw that when plugged in the only light that wouldn't turn on was the -5V. at the time i thought how i found the problem and quickly went out and bought another anted power supply. i remember coming home and testing the new power supply and also seeing that the -5V light didn't turn on. thinking how it's impossible that that power supply is also defective i put it into the system and it worked. since i lost the receipt of the original power supply i can't return it under warranty. but now i'm not sure if the power supply is broken or not. is the -5v light supposed to turn on or not? how can i diagnose the problem with this power supply. i'm afraid to put it in another system in case it burns anything.

thanks.

 

[Bob Anderson]

I doubt if many modern PSU's provide any -5 voltage at all. What you need to do is look up your power supply on the manufacturer's site and confirm if it does or does not supply any -5 voltage.

My Antec smart power 500 does not, because modern motherboards don't use it anymore.

-Bob

 

[peter2679]

thanks for the quick reply.

that's funny for you to say because i just picked up this old computer a friend of mine thought was dead. i actually got psu, case, mobo, cpu, with an older 20 pin power supply and when i plugged that psu in the tester, the -5v lit up.

so what problem could the power supply have if the tester doesn't pick it up? maybe a current problem?

 

[Bob Anderson]

Originally posted by: peter2679
thanks for the quick reply.

that's funny for you to say because i just picked up this old computer a friend of mine thought was dead. i actually got psu, case, mobo, cpu, with an older 20 pin power supply and when i plugged that psu in the tester, the -5v lit up.

so what problem could the power supply have if the tester doesn't pick it up? maybe a current problem?

What I am saying is that your 24 pin power supply doesn't provide a -5 voltage, because your modern motherboard doesn't need it. The older computer you tested does, so your power supply tester shows that it is supplying a -5 Voltage.

That is all there is to it.

Look at it this way: you have two perfectly good 24 pin power supplies.


-Bob

 

[peter2679]

man you really made my day saying that. when antec told me i couldn't get the psu fixed, i got so disappointed and a little mad that i wanted to throw it out the window but i didn't because i really couldn't accept it's death. Now it's just another piece in building another decent computer. maybe i was a little hasty in buying another psu.

thanks again.

 

[Ice Czar]

-5V rail was removed from the ATX12V spec as of version 2.01 if I recall correctly
most any 24pin PSU wont have it unless they felt some compelling reason for backward compatibility

Standard Output Voltages

-5 V: A now archaic voltage, -5 V was used on some of the earliest PCs for floppy controllers and other circuits used by ISA bus cards. It is usually provided, in small quantity (generally less than 1A), for compatibility with older hardware. Some form factor power supplies such as the SFX no longer bother to supply it (systems using the SFX power supply are intended not to have ISA bus slots).

and that archaic is at least 6 years old making it more accurate to say ancient

most of the time a simple glance at the connector is enough, there will be one wire\pin missing
(no white wire at pin slot 20)