Can I use an old power supply?

**purple_car** · 06-17-2004, 12:44 AM

I have some old power supplies from Mac LC475's kicking around and I'm wondering if I could use them with an inverter to power a modern motherboard.

The specs (I need explanations of what they mean cause I'm a newb) are:

output of +5V at 3.75 A, -5 at 0.075A, and +12V at 0.78 A.
input of 100-240V, 50-60 Hz, and 1A.

Thanks !

**STI_FFY** · 06-17-2004, 10:18 AM

Originally Posted by purple_car

I have some old power supplies from Mac LC475's kicking around and I'm wondering if I could use them with an inverter to power a modern motherboard.

The specs (I need explanations of what they mean cause I'm a newb) are:

output of +5V at 3.75 A, -5 at 0.075A, and +12V at 0.78 A.
input of 100-240V, 50-60 Hz, and 1A.

Thanks !

Most modern motherboards need an ample 3.3 Volt rail. This seems to be absent from the specs you listed.

**fantomas** · 06-17-2004, 10:52 AM

looks like a 30 watt PSU. and yes, you will most likely need the 3.3v rail for the modern ATX mobos. so its not going to work for ya, i dont think.

**purple_car** · 06-18-2004, 01:07 AM

wicked, thanks for the help. So how do you tell it is a 30W, and how do you tell if a PSU has a 3.3 volt rail. And what exactly is a volt rail.

Thanks for the help.

**fantomas** · 06-18-2004, 01:17 AM

if it doesnt say 3.3v anywhere...it doesnt have the 3.3v rail.. to get the wattage you do (volts * amps = watts) so (5 * 3.75 = 18.75) plus whatever the 12 volt rail came to. if i remember it was under 30. but now that i think about it, that might be low. the INPUT to the PSU says 100-240 @ 1 amp...which would be 100-115 watts in america (at 100% efficiency) so at say, 30% efficiency, it would be 30 watts. which seems low. im actually pretty tired. lol...hmn..i think i'll try this again in a few days when my brain isnt fried (i have finals tomorrow and am going away for the weekend).

does the PSU say anything about total watts on it?