Will a power supply run if it is not connected to the motherboard (just video)

[DougoMan]

I need some extra power for a video card, and was thinking of just connecting an extra power supply to it until I get something more powerful for the whole system.

Will this work?

 

[hdfxst]

yes you can get this http://www.performance-pcs.com/catal...ducts_id=21193 or jump the green and black wire and use the on-off switch on the psu

 

[Meghan54]

Yes, you can. Just make sure the secondary power supply has no minimum load required on its minor rails.

There are adapters already made for what you want to do. If the two power supplies are close together, Lian-Li made this adapter:

http://www.performance-pcs.com/catal...ducts_id=21193


If far apart, or you want to be able to control when the secondary turns on and off, there is this "home brewed" solution:

http://www.performance-pcs.com/catal...oducts_id=4057

 

[DougoMan]

yes you can get this http://www.performance-pcs.com/catal...ducts_id=21193 or jump the green and black wire and use the on-off switch on the psu

So if I jump the green and black, do I just do it briefly to start it or does there have to be a constant connection?

 

[Meghan54]

So if I jump the green and black, do I just do it briefly to start it or does there have to be a constant connection?

Constant. Try the paper clip trick, then remove the clip without turning the ps off via pulling the plug. It'll die immediately, which is why you were shown the two premade alternatives.

 

[hdfxst]

it's a constant connection.there's videos on youtube if you want to see it done before you try it

 

[tomoyo]

It's funny to me, they actually did this in frys where they hid a power supply under a shelf, and had it attached to like 15 fans to show fans running in the store. I had fun stalking the fan power leads to figure out where the power supply was hiding.

 

[BrianTho2010]

All above suggestions are good, but as another poster mentioned, you may run into issues with a high load on the 12v+ rail and no load on the 3.3 and 5v rails. To get around this you can place a decently sized resistor between the ground and positive leads on the 5v and 3.3v lines from the 24 pin connector of the secondary psu. They will generate some heat, but it will solve any cross load issues you might encounter with the secondary PSU>

That said, most well built power supplies should have no issue having no load on the 3.3 and 5v lines.

 

[mindless1]

Group regulation can be an issue. I disagree a little with Brian that "well built" PSU will monitor and shut down if 5V rail rises too high as it adjusts to 12V load. Many PSU are in fact rated as requiring a certain minimal load on the 5V rail even if they "might" work without it.

Typically this load is spec'd as 1A, IIRC. Doing the math, 5V/1A = 5 ohm resistor with 5W dissipation, to manage heat easier step up to 10W resistor value. It would be easier to keep cool if you use a sandstone/wirewound type and strap it to the PSU intake or exhaust with high heat resistant strapping, or some are embedded in an aluminum shell that you can bolt or screw to the PSU casing inside.

As for shorting green wire to black to turn it on, yes that will turn it on but then there is the issue of it either always being on or you have to manually turn it on before you turn the PC's main PSU on every time which is a bit undesirable? A solution to this is to electrically connect the green PS_On wires from both PSU together. That way, when you press the case power button the motherboard pulls both lines to ground and keeps them both running. An alternate method would be that the main PSU powers a relay that shorts the 2nd PSU's PS_ON green wire to ground when the PC is turned on via the case power switch.

Also, it would be a good idea to connect a ground lead between the two PSU so you don't have a ground differential causing ground current across the video card.

 

[zebrax2]

http://www.hardocp.com/article/2011/08/24/black_art_dual_psus_in_your_enthusiast_pc/1

Posted a few days ago