PCA Forums

Im building a new system, (case and all) and i want to twink it out with all kinds of gizmos, I want to install a 2nd power supply. i have them both in the case, but of course there is only one place on the board to plug it in...If i plug the 2nd one in and have it hooked up with the power on i get nothing, how do i turn it on without having it plugged into the board???

you have to trick the power supply into thinking the ol' "on" switch has been clicked. you do this by sticking a metal object, such as a paper clip, into two of the female ends on the ATX power connector. I don't remember the exact pins that you have to short, but I am sure there is someone here who has that bookmarked -

once you short the pins, it thinks it is on and happily supplies juice whereever you want it

WELCOME TO PCA!

you can also get one of these: http://www.kdcomputers.com/eui/prime/pr ... ponent.htm

another option is once you find those 2 wires, you can splice them into the PS you have pluged into the main board.

I had a board with dual power plugs. best of both worlds.

Greg

Power supplies need a load on them and two pins on the mobo connector shorted out.

It is NOT a good idea to power up the powersupply without a load on the 5 and 12 volt buses - you can damage the powersupply. Some fancier PSUs will not turn on unless they detect a load.

You can use the second PSU to power hard drives, CDs, fans, etc but DO NOT connect both PSUs to the mobo at the same time (you may be thinking about splicing the two PSUs into one mobo cable for instance - DON'T DO IT - you'll fry the PSUs).

There's information here on how to "Hot wire" a PSU:
http://www.compute-aid.com/atxspec.html

I would think it would be safe to splice together the two Power-on wires on the two PSUs so when you turn on the mobo, both PSUs would fire up (again make damn sure there's a load on the 2nd PSU!).

You should also make sure that at least one of the common (black) wires are spliced together between the two PSUs so they share a common ground (don't rely on the metal chassis to carry the ground).

FP-

the item listed above by nexus7...its description is:

Allows quick and easy testing
- Built-in 25W 5.4 ohm load to
generate steady outputs
- POWER_OK green LED indicates
power supply is working
- +5V, +3.3V & 12V leads for volt
metering to check output voltages


would that be good enough for a load to make it safe? this would be exactly what i'm looking for as well. i have tons of 200-250W PSU's laying around that could be used for powering fans, etc in a new case. hmmmm.

Yes that works fine for testing. I have one myself - use it to test customer PSUs.

It's just a mobo PSU connector with an LED on it (which only tells you the 5 volt bus is working) and a big high-wattage resistor to act as a dummy load.

so it wouldn't work to hook that up to actually use it in a pc...allowing you to turn it on and also have a load on it (to keep it safe).

?

Sure I suppose you could, but I think a hard drive or two would be a sufficient load also. That dummy load is just a big resistor and it's going to get warm. I don't see the point of adding a heater to the case.

true. i would like to use an old 200 or so watt PSU to power all the modding equipment...lighting, fans, etc...so a safe plan would be to short the two wires needed...and then put an inline switch in it somewhere so i can control all the mods with a separate on/off button.

That should work. I think if all the aux fans were running off of it at least that it would be enough of a load.

Just get some good old AT PSUs... dont need to do anything to them to get them to work!

Read this . It is very detailed and easy to understand.

nice article, matt

Thanks for the help everyone, works like a champ now...

Originally posted by Pugsley
Just get some good old AT PSUs... dont need to do anything to them to get them to work!

That's what i was thinking...AT PSUs RULE for these sorta hacks.