grrr_arrghh

Hi.

I have an old 300W ATX power supply and wondered if it was possible to use it without connecting it to a computer.

I know for a fact that some of the wires going to the motherboard connection have some current flowing through them (even when the computer is switched off) because various LEDs on motherboards are lit up.

Also, when the power switch (PTM or PTB?) on the computer case is pressed, the power supply starts up (even though the switch is not connected directly to the power supply).

So, how do I get it to start without connecting it to a computer, and what sort of current can I get out of it?

Thanks

Tim

pheer

You just need to connect pin 14 to GND, pin 16 for instance.

Typical values can be 25A 5V, 25A 3,3V and 15A for 12V

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gerty

Since it's a switching supply you'll need to put a load on it to keep it stable. A load of approx 1a on the 5 volt output should do it..

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gerty

andrew2022

i got one 2 stay on by putting a switch between the green wire and a black wire from the m/b connector

Optikon

Generally speaking, what gerty says is correct. My understanding for ATX style standard PC switchers, almost every supply rail has a minimum load requirement. I'm not sure about the switch idea perhaps that is just a shutdown signal (I dont have the spec in front of me) but you will want to put a load on all rails. The minimum load is usually printed somewhere on the box that shows the power ratings..

Sebi

The ATXPSU contain two supplyes: one "standby" supply, this give 5V for part of motherboard and exist when the power cord plugged in. (and if the wall socket not dead...) The standby supply also give 24V for driver IC of main supply.
The mains-supply work when the PS-ON pin connecting to GND.
And need min.1A load on 5V output as Gerty suggested, because the voltage feedback for controller chip coming from 5V.

ante

You can read all about it here:
http://www.pavouk.comp.cz/hw/en_atxps.html

Ante :roll:

pike

Seeing it as ATX, the motherboard power connector should have 20 pins. A green wire is in the cable connector. Short the green wire towards ground (black wire). This switches the main circuit on and you have 12v with decent current.

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BJFroggy

Don't you got any power in yo house?
BJF

TekNoir

Here are two pages that discuss converting a personal computer ATX power supply into a useful benchtop power supply. The first contains an overview of the author's own conversion process along with some tips on the procedure. The second contains an instructional step-by-step procedure for the conversion itself.

Perhaps they could be of some use to you.

http://web2.murraystate.edu/andy.bat...owersupply.htm
http://www.wikihow.com/Convert-a-Com...b-Power-Supply

sam2

Im using a 250W atx , but I had to put a 2 amp load on the 5V ( regulated) rail to to keep the voltage up on the 12v rail, while its under load. At 7 amps the 12v rail drops to about 11v. I tried one 25w power resistor first as the load ,but it got very,very hot ,even at just 10 watts. I ended up putting two 25w resitors in parallel in an enclosed alum. heat sink on the top outside of the case, and now its just warm to the touch.
It works well, and was fun and cheap to do , but if you are powering anything that requires a sudden inrush of current , the power supply will shut itself down. I think that is typical of this type of power supply.

RODALCO

Use a 12 volts 21 or 55 Watts lamp on the 12 volts rail as a load.
It will give you a visual indication too if the supply is working.

Of course you can use power resistors too.

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AFTECH

hi
you simply just connect green cable to one off black one in big connector that connect toyour motherboard this green cable named as soft power on
goodluck!

Sceadwian

I get good regulation on the 5 volt line of my rigged ATX supply with only a 20ohm resistor.

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