Take a Look Inside a ATX Computer Power Supply





Introduction: Take a Look Inside a ATX Computer Power Supply

Have you ever wanted to see what's inside a computer power supply?
Well here's your chance.

P.S. this is my first Instructable so I hope it's good enough

Caution: Don't do this at home unless you know about the risk of shocking yourself even after turning it off! If you want to take that risk, Always discharge those 1 or 2 large mains filtering capacitors by jumpering the green wire in the 20 or 24 pin ATX plug to a black wire in the same plug while the PSU is unplugged. You should hear a click. Remove the jumper and disassemble.

You might want some rubber gloves to keep your hands from getting electrified

Don't forget to rate if you like it and comment, I accept constructive criticism

Step 1: A Look Inside the Power Supply

This particular power supply has a un-switched output meaning the output always has voltage. the rectifier down the bottom of the psu uses 4 diodes to change AC to DC. On the primary side of the board, we see the X-Y caps dominate the space. They serve as the mains filters. Lower down, just to the right of the torroid, are some yellow rectangles. These are caps designed to help the power supply handle surges and inrush current. To the right of the fuse is another inductor (the white thing) used for more mains filtering. It may actually be an isolation transformer. In the middle, we see the heatsinks. attached to them are the mosfets, used to raise the frequency of the AC. This allows the transformers to be smaller, and results in less ripple to be filtered out. On the upper right is the voltage regulating parts. On the heatsinks are more Vregs. On the upper right is the secondary side, with its filter capacitors and inductor.

Step 2: The Output Cables

The output cables are the wires that run from the psu to the motherboard, harddrives, cd drives, floppy disk drives and sometimes to your graphics processing unit (GPU). If you wanted to use the power supply outside of the computer for testing temporarily like watercooling systems and peltiers or permanent things like bench-top power supplies, you would need to jumper the green (signal wire, on/off) to the ground in the main power connector to boot the power supply. When the power supply is plugged in, the purple wire in the motherboard connector is LIVE (5v). This is the motherboards standby power source.

Thanks for looking at my first instructable.

Thanks to tech-king and Goodhart for being a collaborator and helping me to update our instructable.



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    Everybody else just warns about the capacitators, but here we have clear, easy instructions how to neutralize the danger, eg. discharge them safely. Bravo!

    I have opened many power supplys, well 2, but i have never gotten shocked, i don't know why thought, lol

    That's because the big capacitors were discharged...

    i know, its called being lucky thats what...

    I've got about 10-20 old ATX's lying around in a cupboard somewhere

    With great number of power supplies, comes great possibilities. (with apologies to Stan Lee, LOL!)

    Haha, or just being good.

    either way hes should be thankful.

    it's only 250 watts, (whats that purple thing?? ooooo.) *sizzzzle.

    Doesn't matter what wattage.. It's the storage capacity & voltage potential of the filter caps. Granted, they're only 200-400uF, but the working voltage (anywhere from 200 to 400WV. That WV is short for Working Volts!) Now, they may not be charged to the full working voltage, but they still kick you with only 110V. Now, usually, it's not the outer case of the caps, they're usually insulated, but sometimes the regulators on the first heatsink carry some of the potential in DC voltage. (the one closest to the filter caps) Hence the warning on some supplies, that the heatsink may cause shock. 2nd rule of thumb.. If you don't touch it with a volt meter first, Don't touch it with your bare fingers! (and those big high voltage test wands is a bit overkill.)