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Thread: Dual PSU

  1. #1
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    Dual PSU

    Anyone tried this?
    http://www.benchmark.co.yu/forum/att...achmentid=7558

    1. Any problems with overvolting?
    2. Can you connect 2 different types of PSUs (both ATX)?
    3. If both PSUs have switches do you use then only master PSU's switch (and on slave's it is always ON)?

    Thanx!

    EDIT: Forgot to add the link.
    Last edited by aca; 07-05-2005 at 03:56 AM.
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  2. #2
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    try this should have the answers for you
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  3. #3
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    I finally added the right link.

    Just want to know if anybody has already tried this and if it's 100% safe.
    Just 'cause you feel it, doesn't mean it's there

  4. #4
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    wtf?
    i didnt even know that was possible

  5. #5
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    Thanx pancake for the link. I had only the pic from that link though.

    Yeah, it's possible... just will have to see how it works in a week or two.
    Just 'cause you feel it, doesn't mean it's there

  6. #6
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    You can do this trick with a molex connector as well, you just take the green wire from the slave psu's atx connector and hook it to a ground on one of the primary psu's molexs.
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  7. #7
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    @lalPOOO: I think that would be the easiest way to do it. Thanx!
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  8. #8
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    well, if you want to get 2 PSUs working in dual mode all the time, I think it would be wiser to connect the PS-ON wires teogether!

    I have tried connecting a Codegen (absolute PoS) 350W (the chinese type of 350W) and a great AOpen 300W (which is a lot better than that Codegen BS) and I had no problems whatsoever! It actually increased my overclock

    Now I have a 420W Thermaltake PSU which is enough for my sig system.

    I have read an article about combining two PSUs in one case, and divinding +12V and +5V lines (they are on the same line, that's why +12/+5 Volts are never both good, it's either +12 higher and +5 lower or vice versa). They are in Russian and I can't seem to find the links, not that anyone of you (except for aca maybe) would understand
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  9. #9
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    I've heard that that is not the healtiest thing to do to your PSU, as there is no load on the 5v and 3.3v lines for PSU #2, and switching ATX PSU's are designed to operate with a load on all rails. cooler master included a dual PSU harness with my CM stacker, all it does is connect the "power on"(green wire) and a ground wire to the second PSU in order to give it a simultanious power on signal.

  10. #10
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    The only problem I heard about all this is something about overvolting. Nothing else. But noone has confirmed this. I would like to see what somebody (who has tried this) has to say. I want to be sure before I connect the 2 PSUs.
    I would use the better PSU (master) to power the MoBo and graphics card, and the slave PSU for avarything else (2 pumps, hdd, dvd, few fan controllers, fans and other gadgets).

    @Bergo: You are saying that this is only bad for the slave psu, right?
    Just 'cause you feel it, doesn't mean it's there

  11. #11
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    The problem using two PSU's is that they have to be 100 % matched.
    Otherwise one will try to either lower or increase the voltage, while the other one will try to do the opposite.

    And as previous stated, using the PSU without load should only be done for 2-3 seconds.

  12. #12
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    I use two power supplies on my bench/gaming rig. One powers the motherboard and all drives and graphics card. My second one powers my watercooling systems. This allows me to shut down the computer and continue to circulate water through the waterblocks to cool the system down much quicker. I have a jumper in the correct pins to power the second supply whenever I turn the switch on the back ON. Works fine. I've even used the second to power the video card on occassion. I don't know where all these Electronic Engineers get their info but you do not need a load on a power supply and running two is really no different than running one. Just make sure its set up correctly. I have mine different than some so don't go by what I do but its very simple.To say this though, one Power Supply should only be used to power the motherboard. DO NOT splice wires together to "Combine" them. That is a big NO NO. You will likely fry everything. But using one to power extra drives, fans, video card is ok, just make sure the secondary PS starts with the primary. There are a two wires to connect between the PS's if you do it that way.
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  13. #13
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    Ive done this. Not so clean, but i used a 650watt to power my dual CPU rig, fans, and system drives, then a 430watt PSU to power just the RAID 0.

    The second PSU was simply turned on by a radio shack switch, with 2 wires running to the green and black ground.

    No problems at all. Had to do it because 1 PSU would blow if i powered the rig with it

  14. #14
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    I have done this for about 2 weeks, when i upgraded and the 400w wasn't pulling it, it was running till I got a new one. I just did the always on way and unplugged it to turn off. I used the master to power mother board and the slave to power drives, fans and the molex connecters of vid card.

  15. #15
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    The PSU unit is both simple an complicated at the same time.
    Simple because users thinks it is simple, to transform voltage.
    Complicated because they are.

    Testing it without load is not recommended, and will / could give false voltage readings.

    With so many PSU brands, they all differs from one another.

    Finding a good professional test report is difficult.
    And I mean, not this - "I tested it and it worked flawless".

    Instead of talking about max Watt, we should discuss how much current the PSU can deliver on the vital voltage rails.
    And the correlation between the +3.3V, +5V and +12V.

    Thoughts on 650W Silverstone ST65ZF-GM SLi before I buy it.

    Edit, Minor update.

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    Last edited by Esso; 08-23-2005 at 08:11 AM.

  16. #16
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    This is generally pointless and dangerous.

    Connecting two PSU in paralell even if they are the same model will create a more unstable voltage in most cases.
    This is because as the load fluctuates the PSU's will try and compensate to keep the voltage stable.. but they will do this differently and if there is any PD between the PSU then you might get them "shorting" against each other a bit, especially if they cannot equalise the lines (if 12v and 5v are combined on bother PSU this is likely)

    This might just mean a less clean voltage, but it might blow up one of the PSU.
    If your PSU blows up you might kill other components.

    The same is true for using a second PSU to power hard disks or graphics cards, except in this case you may get current flowing through IDE cables or the motherboard between the PSU where only small amperage is permitted... this might kill the HDD, graphics card or motherboard.

    The only safe way to run two PSU is to use one for all components that connect to the motherboard and just use the second PSU for fans and watercooling... generally thats not worth the bother.
    Or if your powering peltiers, but even then I recomend a dedicated unit.

    If your PSU is not doing the job just buy a newer better one.
    Messing about with dual PSU probably wont help you... and might kill your stuff so dont bother.

  17. #17
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    The links shown at the top are safe.. its not running the PSUs in parrellel.

    I did this wehn I lost a 300 W PSU a couple years ago
    I used a 110W to power the board and a 90W for fans and 2 drives.

    I actually found this thread looking on ways to use caps or resistors to run 2 different PSUs in parrellel or at the minimum combine the dual rails on a crappy PSU

    I took a 36" wire cut it in half stripped about 1/8th inch off each end . I jammed one the wire into the top of the ATX connector on each PSU (14 to 14 15 to 15) super glued it in place and ran that for 18 months or so with no problems.

    I will let you guys know how my 400w and 450W mod goes (Doing a little more then just he wire though)

  18. #18
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    I simply connected my two power supplies (Tagan 580 EasyCon and OCZ Modstream 520W) by using the cable which came with my Stacker; it is used to add a second PSU to the system by starting it at the same time you hit the power button, (Green and Black cable).

    So I use the Modstream for my X1800XT, 2 HDDs, pump and soon also a couple of fans. The Tagan power supply is dedicated to the rest of the system (basically Motherboard/CPU/DVD).

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  19. #19
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    i think they have a thing that combines the atx connectors [too sick&dizzy to post link] i can barly type strei ght

  20. #20
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    Quote Originally Posted by D4nnyOcean
    I don't know where all these Electronic Engineers get their info but you do not need a load on a power supply and running two is really no different than running one.
    The "slave" PSU may need a load depending on its make/model. Not all need a load, but some do.. and not all rails need loads, just some. When running multiple PSU's as shown in this thread they should not be electrically joined other than the startup wire.

    Some work is required to run PSU's in parallel..
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  21. #21
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    Wow that's easy... I knew it was possible but I never thought it would be that simple. Thanks pancake.
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  22. #22
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    Here is a dual psu guide if your interested..

  23. #23
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    Quote Originally Posted by Freebo
    Here is a dual psu guide if your interested..

    thanx, I´m looking 4 a guide like this ...

  24. #24
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    As has been pointed out, this is not about running PSUs in serial, butr a simple guide on how to make multiple PSUs start up and shut down automaticly. Very very useful for extremist systems that often use way more amperage than a single PSU can handle (atleast if you dont wanna spend 250$ on a PSU)...

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  25. #25
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    oh, then use a relay on the green wire to ground and set the 1st psu [the one connected to the motherboard] to the electromagnet in the relay,

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