Guide dual psu and test psu : a how to guide.

hello fine people of the forums.

well this is one of my few posts here (could be my 1st i signed up ages ago and can't rember if i posted then)

thought i'd do a little guide for you all as i did say i would. well i did on cpc but sod it, it's going here 1st!

Off the bat my discalmer!

This guide is under taken AT YOUR OWN RISK!, all damage to yourself or your kit is your own fault, I nor the good people of bit-tech can be held responsable,

BASICAL IF YOU MESS THIS UP, GET SHOCKED OR DIE IT'S YOUR OWN FAULT!

Ok thats that,

In this guide i will be doing two things.
one is a guide to making a test psu. this can be used if you don't want to bugger you pc up after you just solded something up or made somthing for a mod for your pc.

the second is how to dual psu, this is for power users or people who just think its cool. like me

Well on with the modding!

You Will Need:
1) A psu, or two if you want dual PSU's!
2) Screwdriver. Phillips head.
3) Electrical tape or heat shrink.
4) soldering iron (not really needed but you can use in for this mod. i'll sya were but to be honest i didn't use one this time)
5) Wire cutters.
6) A paper clip.

NOTE: The psu i use insted of a green wire they have a gray wire. i have no idea why.

TEST PSU (If your doing dual PSU's you need to do most of this too, this bit for the dual psu people is how to make the slave psu)

1, Get your PSU and test if it works. to do this get your paper clip and short the green wire and any black wire on the ATX plug together. You may need to attach something to a molex as some psu won't work without a load so put a cathode or somthing.



The green and black pins to short are in this pinout.


2, Right if you psu don't work. then you stuffed and you need a diffrent one. BUT! if it works then you need to let it discharge. The thing with PSU's is they can store a migty charge which really fu*king hurts and can kill. so leave the PSU unplugged overnight to let it discharge. then in the morning short the green and black pins again just to make sure.
ok, now it's time to bust open you psu. grab a screwdriver and remove the 4 screws from the top (if your not using a ATX psu then you'll have to find then, but for most ATX psu the screws are on the top of the psu) you may only see 3 but this is becuse most companys put a sticker overone to know if someone been messing with it. so just peel of the stickers if you can't find the last screw. then remove the cover from the top.


OOOOWWWW!

3) From the stx plug end cut the green and black wire show in the pinout (above) as close to the atx plug as possable. then cut off the rest of the wires to as short-ish as possable. cut the wires so they are about an inch or two long from the PSU's pcb. Right, stop here. look at the atx plug. there should be two wires that go together. For me it was two wires going to pin 11. make sure you connect these two wires together other wise it won't work. they should look like a thin orange wire and a big orange wire. just connect them and your sorted. As for the rest of the wires you can do a few things. you can cover each end and then zip tie away somwere or you can use heatshrink to cover the ends, you can un-solder the wires from the psu. you just need to get rid of then or tape up the ends. MAKE SURE YOU COVER EACH END OF THE WIRES OR MAKE SURE THEY CAN'T TOUCH> IF NOT YOU WILL SHORT SOMTHING!!!!!!!!!!

what i did was to cut all the same color wires a diffrent length then taped each end up. then taped the wires away and was done with it.
Like so,


Wires all cut to diffrent lenghts then each taped up.


all the wires taped up.

WARNING!:
However don't do what i did and try to cut the wires from the board with a knife. as you can slip.


MY THUMB! :cry:


Ghetto Bandage!

4) OK, so you got all you wires taped up and they should be inside the psu apart from two long wires. the black and the green. now turn the psu upside down and shake it like mad. hit it everything. you want to get anywire bits out so it won;t short. Now get the top and put it back on. screw it all shut and test the psu again. with the long black and green wires cut a little sheeth from the end to exspose wire and with the psu plugged in and with a load touch the wires together to see if it will fire up. if it dont then er........hm........cheack the wireing again. if it when bang then unplugg it CAREFULY and chuck it before it kills someone but if it works then have a cup of tea.

(DUAL PSU PEOPLE, YOU WANT TO SKIP THIS!)

5) Now that everthing works all you need to do is add a switch to the green and black wire, then fine somewere to put the button. i suggest using a set of spade connectors for a switch and mount the switch on the top of the psu. that way you can get into the psu by slipping the spade connectors off the switch.



Seeming as this a test psu you've just made then you may want to mod it. get a cold cathod light grill for the fan and an LED fan. plugg that into the molex;s of the psu and this way it acts as the load. that way you don't have to plug stuff in to make it work. Now sit back and marvel at you test psu.

Duel PSU's (Conti form step 4)

5) With your psu all done and full working get your master psu (One you want to run the mobo (should be a good one). Find the black and green wires again on the Mater psu ATX plug.



right either snip that somewere or use a exstraction too to get the wires out of the ATX plug. IF you do this then you can cut the sheeth of the wire without snipping through the wire and use heatshrink so it looks neater but is dosen't matter too much.
Anyway, you've got the green and a black wire and snipped through then. Remove some sheeth from the green wires ends and twist the wires together with the green wire on the slave psu (the one yo just cut up and put back together).



twist those wires togther and solder together if you want. it;s a good idea to do this as it's much better than the twisty-twisty wires with a bt of tape on them. Stick some heat shrink or tape over the green wires then do the same with the black wire.

Now you should be done, all you got to do is test it. put a load on each psu and short the green and black wires again and it should fire up. you need each psu to be plugged into the mains by the way too,



and there you have it. 2 psu working as one. isn't lovely. the only problems i've ever had was if you turn one psu off or unplug it the other one comes on. a little annoying but thats what happens. just means you always have to turn the psu's off at the wall.

ok well thats it.

all the guides i've done before can be found here :

 

Looks good. I wont try it until someone else posts and says they have success.
(I could die!) I've got a few PSUs lying around, so will definately setup a test PSU for component testing...

 

all i do for a testing psu is leave a solder a green wire to a black wire (there should only be one green) and then when i flick the switch at the back of the PSU, it switches on!

 

i've built dual psu systems with no problems before. in fact my main rig is dual psu. a 600 for pc itself and 250 for other random stuff,

 

You also need to short the thin brown wire to an orange wire on most PSU. Also, you say cut the same colour wires to different lengths to prevent them shorting - on all but the best PSUs, the wires are conencted together on the circuit board, but on any PSU you can connect same colour wires together with no ill effect. Otherwise good guide, apart from the fact that you really don't want plastic tape on/near the heatsinks. Couldn't you snip them off the board?

 

Is it possible to use those dual psu's in one system where: Psu1 would supply power to the motherboard and a few drives, and Psu2 would take care of alot of other drives. So as an example I have 12 drives totale. I would have motherboard + 4 drives sayon psu1 and on psu2 the othere 8 remaining drives.

I'm really curious towards this, cus my common sence tells me that eventually you would get discharge between both Psu's.
Can anyone prove this? Maybe even a solution ? Like a schematic to to combine volt rails via Mosfets orso .

 

I think that as long as you wire the grounds (black wire's) together you shouldn't have any problems. But I'm not 110% Sure about that.

 

Neither am I.
Suppose you have 12.2V going to your motherboard from psu1 and 12.4V going to some drives from psu2. (Not sure bout this) but the IDE cables share these voltages ? and therefore get 12.2V and 12.4 on the same line resulting into fireworks ?
I'm in need of a solution.

 

AFAIK the IDE lines have no power lines, so you should be ok. What you REALLY don't want to do is power your GFX card and motherboard from separate PSUs.

 

thanks for the input . Btw I just got back from a lan, and talked to a guy who did the exact same thing. So i guess it's ok.

 

I have a legacy machine that runs on two PSUs-- One is Motherboard and the lower two drives, and the other does all other peripherals.


I'm only scanning the article, it looks like a no soldering mod? If you want to eliminate that whole one PSU powering up when the other is shut off thing, then wire both PSUs to the same switch on the master. In fact, it wouldn't take much to just wire the second PSU into the first so you need only one power cable.

Mine are AT PSUs, I have one hardwired on and a jumper cord going to the "Master" PSU, so when power is apoplied to the master, it applies power to the slave. I desoldered the motherboard wires and substituted some additional peripheral power cables in the slave PSU. If I need to run min-config, then I remove the jumper cable between the two PSUs.

 

I fried an enermax 330 watt PSU on a crap Dell motherboard (not realizing it had proprietary connections), which was out of my main PC so I rigged up a 200 watt ATX PSU to run my system with a 250 AT relayed off that running my drives/fans in a dual P3 system, ran that way until I got money for a new power supply...

 

Wow, just did a 'bench PSU' today, and NOW I saw this post. lol

I was trying to plan the voltages and have the plugs all set up, but after a quick matrix showing up the voltage possibilities, I decided to just use a plug for each 'wire' and off I went meking holes everywhere on the PSU.

Of course, the thing would not close (known as 'lack of planning') because of the fan, but I put the fun on the outside and Ta-Da! lol

It seems to be working, based on the multmeter tests, but never got to use it yet.


My next mod will have dual PSUs, only I will break the green wire and put on a switch in there. So the second PSU will work only if the switch AND the main PSU are on.


Thanks for the tut, though I saw it a bit late. lol

Best wishes!

 

Er... No edit?

Could someone tell me why I get NO results getting a voltmeter and putting the red wire on the positive of a battery and the black wire on the negative of another battery, with no connection between the batteries? (or vice versa on the wires)

I mean, if there are electrons trying to get out in the negative of a battery, and the positive of the other battery wants electrons, why there's no current flowing?

 

A battery does not store excess charge, it is electrically neutral; it just has a portion of its electrons chemically segregated from their respective positive ion counterparts. In order to get current from one terminal of the battery to the other, a complete circuit must be made from one terminal to the other.

When two batteries are involved, then the "free" terminals must be connected to complete the circuit.

 

It still seems so magical to me... lol

But I tryied it with the PSU too (12V to ground, literally), and no results...

Anyway, thanks for the tip!

Best wishes

 

Oh, it's Pure Freakin' Magic... don't let anyone tell you differently.

One of the magic things about PSUs is that some of them need to have a certain amount of load to them-- they won't put out the right voltage levels until there's a minimum amount of current being drawn.

 

yeah i got a little psu like that too. it puts out 10 or 9v with no load then pumps it up to the proper 12 when needed.

 

Oooh I see...
So that's why 'bench ATX PSUs' use a load resistor?

Just a silly question... For the PSU to pump the right voltage, do I need a load resistor for each power line (ex. +3.3, +5, +12 etc)?

 

Yes to both.