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Electonics questions about power supplies

Last response: in Components
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April 8, 2003 8:24:48 PM

I have a couple of electonics-related questions about computer power supplies.

1. I recently sleeved the wires from my power supply using some <A HREF="http://www.wirecare.com/wc_product_list.asp?prod=PT&pro..." target="_new">wire sleeving</A>. To use the sleeving, I had to remove the molex caps from the wires. I went to great lengths to ensure that when I put the molex caps back on that the wires were in the EXACT same position as they were before I removed the cap. My question is, was this necessary. I mean, obviously it matters for the 12V (yellow) and the 5V (red), but does it matter which order the ground wires (black) are in? If so, why?

2. How does one safely discharge their PSU? I've read that you can remove the PSU's circuit board and run a screwdriver along the bottom of the board to discharge it. I've also read that you can get a 3-prong extension cord and remove all the prongs EXCEPT the round prong (the ground) and plug the PSU into the extension cord (which should be plugged into the wall, thus grounding the unit) and then turn the PSU on and off a couple of times. Do these sound safe? They sound a little scetchy to me.

I'm more curious about a good answer to my first question, but it would be nice to know how to dischare the PSU as I have been considering painting it which would require that I take it apart.
April 8, 2003 8:45:22 PM

For discharging, try unplugging the untit from the wall, and turn your pc on. you should see the fans or hear the pc speaker jump as the mobo uses up the last of the usable charge. Dunno how well this works, but its how I have done it and im still here.

As for the 2 black grounds, I think one is -12v and -5v, check wih a voltmeter. If you get 17 or 7 volts, then its the wrong one, IIRC. Best bet is to consult the PSU maufacturer's site.

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April 9, 2003 1:55:04 AM

1) The ground wires won't matter. They are both at 0 volts and will most likely connect back to the same spot on the circuit board.

2) <b>DO NOT</b> go shorting things out inside the powersupply <b>NOT EVER</b>... Don't even think about it. If you don't electrocute yoruself, you could very well end up feeding the 190volt primary charge into a 5 volt part...

Next time you want to put sleeving on a power supply, get the spiral kind (looks like a coiled phone cord)... it's super easy to use, nothing to take apart, you just hold one end and start winding it over the wires like you would wind a phone cord around your finger. When you get to the end, clip it with a pair of side cutters and do the next one. Here's a link to the stuff: <A HREF="http://cableorganizer.com/spiral-wrap/colored.html" target="_new">http://cableorganizer.com/spiral-wrap/colored.html&lt;/A>


To discharge your powersupply, unplug it from the wall and turn on the PC... the fans will jog a little and then stop which will drain off the secondary charge. Next... wait about 5 minutes before you start disassembling the casing to let the primary charge drain off.

Now the big question... Why are you taking it apart?




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April 9, 2003 3:33:24 AM

Yeah, this method for discharging power supplies is how most people I know do it.

Some people will try to tell you not to turn your power on when the power is unplugged because it could "fry" your motherboard. Ignore all this crap and go ahead. I've been doing it this way for a long...time and most of the computers I did it with are still around (old 386 still chugging away at Qbasic)

It's all good ^_^
April 9, 2003 1:04:37 PM

1. Doesn't matter they are both exactly the same. Every black wire comming from the PSU is a ground with 0 V potential.
2. Plug out the PSU of the electricity net and then start your PC.

My dual-PSU PC is so powerfull that the neighbourhood dims when I turn it on :eek: 
April 9, 2003 4:32:28 PM

Thanks for all the help guys.

Quote:
Next time you want to put sleeving on a power supply, get the spiral kind

I considered the spiral wrap, but prefer the sleeving. It wasn't difficult and everything went just fine...like I said I was just asking because I wanted to know if the black wires had to be put back in any certain order. I went through great pains to make sure I did in fact put them back in the correct sequence, but I could have saved myself some time (and headaches) had I known it did not matter.

Quote:
Now the big question... Why are you taking it apart?

I was considering painting it black (it is currently that ugly gray steel color). I probably won't be doing it though as it seems a little dangerous :tongue: . Mostly I was just curious.
!