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Help With PSU Wiring

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December 21, 2010 5:49:56 PM

Hi!

I'm wiring a 4 pin ATX power cable to a 8 pin Mini-fit to SATA power cable to power my optical drive and hard drives. So....I bought a 4 pin to 8 pin converter. Now, how do I convert the 12v from the 4 pin to get 5 volts out of 8 pin side of the adapter. In other words I want the 4 pin side:

+12v +12v
GND GND

to go output on the other side of the adapter to

+12v gnd gnd +5v
+12v gnd gnd +5v

How do I go about doing this? Any help would greatly be appreciated!

Thanks!

More about : psu wiring

a b ) Power supply
December 21, 2010 6:03:31 PM

Hello,

Is this the adapter you bought ? :



If it is, then you simply have to connect it to your hard drive's power input.
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December 21, 2010 6:17:43 PM

I wish it were that easy! This is the adapter that I bought:



The original setup state which was:

Yellow (12v) Yellow (12v) Yellow Yellow Yellow Yellow
Black Black -------> Black Black Black Black


I rewired it to:

Yellow (12v) Yellow (12v) Yellow Black Black Yellow
Black Black ----------> Yellow Black Black Yellow

I just want to make sure it'll hook up to my mini-fit to sata wire without frying anything.

The setup to that is:

+12 gnd gnd +5v
+12 gnd gnd +5v -----------> SATA power ports


Any thoughts?
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a b ) Power supply
December 21, 2010 6:49:25 PM

What you bought is an adaptor to convert a CPU 4 pin connector to a CPU 8 pin connector. It is NOT made to be a SATA adapter. If you need more SATA power connector, you MUST buy a Molex (4 pin) to Sata adapter, like the one found here.
The adapter you bought is of no use to you. And I don't see how you would have been able to connect it to a SATA power connector...
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December 21, 2010 7:01:24 PM

It does fit....I'm connecting that cable to one from an old Power Mac G5. That cable looks like this:



It's a 8-pin mini-fit molex connector on one end (a female plug) and three SATA power connectors on the other end. So, the adapter does hook up to it....I just want to make sure that it won't short out anythign when I hook it all up together.
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a b ) Power supply
December 21, 2010 7:23:23 PM

Ok, I see what you're trying to do.

In my own experience, trying to connect cable that weren't meant to be connected together in the first place is never a good idea. Do you have the specs for the Power Mac G5 8-pin mini-fit molex connector ? Do you know which ones are the 12v and which ones are the grounds ? Usually, yellow=12v and black=ground.
For each yellow, there must be a ground. Normally, they are one on top of the other : Y-Y-Y-Y then under it B-B-B-B. But do you know which line is which ?
If you do, you simply have to connect the yellow with the yellow and the black with the black. Never connect a yellow to a black or vice-versa ! That will cause a short-circuit.
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December 21, 2010 7:29:33 PM

Yeah....sorry I should've put a picture up of the cable to begin with.

I do know the pinout. For the G5 Cable it's:

Y-B-B-R
Y-B-B-R.

I just want to make sure if I can connect yellow (from the 4-8 pin adapter) to red (on the G5 cable) and it'll be fine. 12v are coming from the PSU, going through the 4-8 adapter and reaching the connector. I want to make sure that when the current crosses over from the 4-8 adapter and into the G5-Sata cable that "red" cables will carry 5v, instead of 12v that is coming from the PSU and through the 4-8 adapter.
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a b ) Power supply
December 21, 2010 8:00:51 PM

No, it will carry 12v. In parallel, the voltage stays the same. If you were to connect everything together right know, there would be 12v in each red wire.

Here is what it would look like :

http://al360ex.t35.com/You%20wiring.jpg

If you want 5v in the red wires, you'll have to use a resistor that will do just that, and ideally connect it before the cables are split. That way, you'll only need 2, whereas if you were to connect it on the brown wire (on the drawing) you'd need 4.
You'll have to connect it on the wires that have 12v on them, not the grounds.

Here's a link explaining how to calculate the value of the resistor you need (it's quite simple) : http://www.piclist.com/images/www/hobby_elec/e_resistor...

Edit : When you click on the link, it will tell you that the page is not found (error 404). Simply click in the address bar and press enter. The image will be displayed. I don't know why it does that.
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December 21, 2010 8:04:39 PM

Ok. Great. I'm assuming this means I'm going to have to cut and solder the 12v wire before the split?

Thanks so much. That's what I was trying to figure out if the "5v" wire in the G5 cable would work as a resistor to reduce the current....that doesn't make much sense now that I think about it.

I appreciate it. Thanks for putting up with me. :) 
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December 21, 2010 9:29:12 PM

Buy a new PSU, with all that you need.

I got a OCZ Fagility 550W Modular for $55.

In responce to below: I forgot to mention that it is a refurbished one...still a good one!
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a c 243 ) Power supply
December 21, 2010 10:01:56 PM

al360ex said:
I don't trust PSUs that are below 80$. There're too often very cheap and break in the first year or so.

That's one of the silliest things I've read in a while.
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a b ) Power supply
December 21, 2010 10:14:53 PM

Well, if you read reviews, you'll very often find that these PSUs didn't pass the tests ->http://www.jonnyguru.com/
I'm not saying that expensive PSUs fare any better. It's simply that cheap ones are more likely to cause problems than a more expensive one from a known brand. If you look here, you won't find a lot a quality PSUs. There are some, but they're rare.
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December 21, 2010 11:55:30 PM

I have a 600W OCZ Modstream. I did my research and it seemed to work well for what I want it to do. It's not an exuberantly priced PSU, but wasn't cheap either. I'm pretty happy with it. If it breaks in a year, well...I learned my lesson. My concern was making a hackintosh that kept to as "pure" in look as possible.
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