What pins need to be shorted to use a dell nps-250kb as an external power supply

Red ,yellow,and orange wires are 12 v 5 v 3 v.

Here is a Dell NPS-250KB,

http://www.justpowersupplies.com/dell-nps-250kb-b-power-supply.htm

This is a cutaway of an SMPS similar to yours,
(Switched-Mode Power Supply),

http://en.wikipedia.org/wiki/File:ATX_power_supply_interior-1000px_transparent.png

In-between the letters B and C, and C and D, are the Heatsinks.

The shiny rectangular block looking objects, are actually aluminum fins, and put together, have a rectangular shape.
They are connected in a row with a thin metal strip.

[DO NOT open a Power Supply plugged into power!
Dangerous voltages inside that can -> Badly to FATALLY shock you!
(Fatally = Kill)

The Electrolytic Capacitors inside are designed to hold a charge, then release it all at once. Power supply unplugged from power, the capacitors inside can hold a charge for weeks, months, sometimes over a year!
They need to be properly discharged before working on the unit ]

I have a feeling you mean towards a Processor's Heatsink, inside a Dell desktop computer.

There are styles where Dell used a type of Thermal Glue, and stuck the Heatsink to the Processor.
A hair dryer set to medium, and slowly swirled around, and around on top of the Heatsink, will soften the glue.

{The above is AFTER the mounting clips are unclipped, that hold the Heatsink to the Processor}

WITH A GLOVE the Heatsink is gently twisted a little, one direction sideways, then the other direction, until it comes loose.

You can feel when the glue is soft enough, to start twisting on the Heatsink. You can also feel when it is not.

DO NOT manhandle it. The Heatsink will come loose, but so will the Processor. You will have a Processor with broken/bent pins on the bottom. This = No.

Or your reference may be to a particular style that Dell used.
This is one of many. Used on an Optiplex G150 desktop computer,

http://support.dell.com/support/edocs/systems/opgx150/sm_en/smdsktp.htm#mphs_assy

(Scroll down)

So what is the Model Number of your Dell desktop computer? Post in a Comment.

Regards,
joecoolvette

Another thing you can do is smell it.

But I got to tell ya, eBay has a bunch of them, for less than twenty bucks.

I've done it, it ain't worth the trouble. You'd be happier buying one from tigerdirect.com


PLEASE RATE THIS ANSWER

Here is a AWESOME guide on converting the power supply to a general power supply (lab). It has all the wiring and voltages.
http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply

You can replace the power supply in this Dell with a normal ATX power supply. Make sure the total wattage is equal to or greater than the old power supply.

Plug the power supply to desire voltage. Monetarily short the GRAY and BLACK wire in one second.

Hi,
SPECIFICATIONS:
Dimensions 5.9"W (150mm) x 3.4"H (86mm) x 5.5"D (140mm)
Special Features Dell Proprietary Main ATX & 6 Pin Auxiliary Connectors
AC Input 100-120V/7A 60Hz 200-240V/3.5A 50Hz
DC Output Voltage 3.3V 5V12V
Total Output Max Load 200W


Regards.

hello bob, try putting a phanton loa on the other bars of the power supply, it seems tha the power supply is not starting, some switchin power supply require an apropiate load to start.

You need to ground pin 14 momentarily to turn the power supply on. Pin 10 provides +12v, pin 12 provides -12v. Diagram here.

its brown or gray which ever is there and the second one is black