Connecting 2 PSUs together

Discussion in 'General Hardware' started by Filth, Mar 16, 2006.

  1. Filth

    Filth Active Member

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    is it safe to do it.... I have LC550W and its unstable like hell.... with my system on load it can hit 12v rail and drop it to a 11,65V!! fans lose ~300rpm.... and the whole system becomes unstable..... resulting in high temp. and artefacting.... no BSOD yet (thank god).....

    so im thinking.... connecting two PSUs togehtetr would solve the problem.... one being for the system and the second one just for the gfx....

    is anyone out there that did this without burning sometnihg up?
     
  2. Why not just get another PSU and avoid the whole hassle? In order to do this you would have to splice all the wires on your 24pin connector to the other PSU's 24pin connector in order to get both PSU's to power up when you press the power button. And besides, you'd have one unholy looking mess of wires in that thing.....
     
  3. Filth

    Filth Active Member

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    i have this link that has a guide how to do this kind of work

    http://www.speedy3d.com/articles/case_mod_p3/index.shtml

    and i dont have the money to buy another PSU.... somethings are more important....:frown:

    and you dont have to do all the wires.... just a simple relay.... and its done.... im just asking if someone did this kind of mod, and how did it work.... :)
     
  4. Pat the Cat

    Pat the Cat Ancient Guru

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    Well, I've done a couple of rigs like that... and I really DON'T recommend it.

    The amount of labour involved in wiring it all up just right is large. The reliability is lowered. And you have the problem of housing 2 PSU's with presumably 2 different mains inputs.

    Bet your life? Really mess up and you could die. Trust your electrical skills that much?

    If you are committed (and this sort of knowledge is useful if you go into rack mounting equipment) then I suggest you try with a few scrap components and plenty of time and space.

    Just doing it as a one off is a no-no. Either you know enough or you don't to be trying that sort of thing.
     

  5. Filth

    Filth Active Member

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    why wiring.... you just connect a relay to a 13pin and G of the second PSU and to a molex's yelow pin and G of the first PSU...... shown in the link above

    i'm going to use the second PSU only for gfx, therefor i need just ONE 12V rail and that's it.....

    the first PSU will power up the usual components (MB, CPU, HDDs)..... with the exception of the gfx which will be powerd with the second 550W PSU I just need exact power on time which is achieved only with a relay.... thats it simple as that

    the question is...... IS IT SAFE for the gfx to be powerd with another PSU??
    as far as I know it should be.....

    http://www.thermaltake.com/product/Power/PurePower/w0099/w0099.asp

    here is the same idea...... another PSU connected to a 14pin and ground of the main PSU for signal to power up.......
     
  6. ViciousXUSMC

    ViciousXUSMC Banned

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    Its a bad idea for a bunch of diffrent reasons, its possible but highly recomended that you do NOT try it.

    Even if you just want to power your video card with the 2nd psu you do remember that it gets some of its power from the motherboard correct? now what happens if you have 2 diffrent sources of power going into the card? I dont know... I dont want to find out. Might nuke somthing, or cause some sort of distortion or emp.
     
  7. Altazimuth

    Altazimuth Maha Guru

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    Haven't we done this already?

    - Using the +12v to only power up the gfx cards means that the other rails won't be used for anything (not loaded). So the second power supply might not start up, or even be damaged.

    - The 'power good' on the second psu isn't being utilised, so it won't be able to tell the mboard logic if it's voltages are out of spec.

    - The Themaltake device is designed for the purpose.
     
  8. Im2bad

    Im2bad Master Guru

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    A one shouldn't do that with a general PSU, use the Thermaltakes additional PSU instead. Don't remember the name though. That should give your gfx it's power.
     
  9. BryanStramer

    BryanStramer Member Guru

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    I would do it.

    A very easy mod.

    Switching power supply circuits are simple. There are probably plenty of guides on the net to help you.

    You are right, a relay circuit would be all you need to trigger your second supply.

    My only concern with such a mod is the noise, heat, and wiring mess inside your case.

    Quote-
    Using the +12v to only power up the gfx cards means that the other rails won't be used for anything (not loaded). So the second power supply might not start up, or even be damaged.

    What? That's not true. Leaving a power supply unloaded WILL NOT hurt it at all.
     
    Last edited: Mar 16, 2006
  10. Crystallas

    Crystallas Maha Guru

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    You beat me to it.
    Lots of unexperienced people are playing expert here. While its quite clear that people are using their theories to give advise. How many have used more than 1 PSU for one system? Ive done it. Its not stupid, but you cant just hook it up without knowing how to do it. Not trying to flame anyone, esspecially when they are trying to make their best educated guesses. But if you have ever had a bad experience with multi PSUs, then you did it wrong, its just that simple.
     

  11. BryanStramer

    BryanStramer Member Guru

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    Amen.

    It is a simple operation for anyone who has fair knowledge of switching power supplies, can read a schematic, and can solder and use a DMM.

    If you can't do these things, then you probably shouldn't.

    But it really is not that hard.
     
  12. Filth

    Filth Active Member

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    so its not wrong or anything to power up gfx with another PSU, as long as its connected properly??

    ok, i'll give it a go..... wish me luck

    and tnx for answers!:)
     
  13. BryanStramer

    BryanStramer Member Guru

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    No, what you are trying to do is a legitimate, well known, well documented operation.

    You'll do fine.
     
  14. Filth

    Filth Active Member

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    i heard that if the other rails (3,3V, -5V, -12V) on the second PSU are not loaded the PSU becomes unstable..... wheres the truth in that??
     
  15. SirkoZ

    SirkoZ Master Guru

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    Well - I had such a system - in times of good old Athlon 1800/1900+ and GeForce FX 5900 LX with 2x Voodoo^2 in SLI and the mainboard, disks and CD-R/OMs had one 300W PSU and the graphics card had its own (though) AT 200W PSU with good ol' 220V power switch. :)

    Anyhow - I switched them on as at the same time as I could and the whole conglomerate worked very nicely...the only "occasional" concern was if the current would somehow go from one PSU to the other, because of the difference in the 12/5V...
     

  16. BryanStramer

    BryanStramer Member Guru

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    None. Not true.
     
  17. Andrull

    Andrull Member Guru

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    I use two psu's in my pc. And they are both connected togheter by myself. 400W+250W. The 250W is only feeding my 6800U, and the 400W does the rest.
    The only thing i needed was to connect two wires.

    The 400W psu is connected to the mainboard, and the otherone is connected to the other psu by, connectingthe little green cable with the other green cable (you can find this green cable on the 20/24pin connector) and the black cable (next to the green cable) with the identical black kabel on the other psu.

    So when i turn on my pc (the normale way) it start up both psu's (since the green and the black is the start mechanism).

    And it's working absolute great!

    One little thing. If i unplugg one of the power cables (240V) the other psu will start turning on/off all of the fan's connected to it.

    This is absolutly no problem for me!
     
  18. Galvecho

    Galvecho Member Guru

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    i have two psus too, i have the bigger one powering my mobo and video, and the other psu powering my hd, floppy, dvd-rom, and my fans, it works fine, you just have to be careful to power the drive psu first, after that you can power the cpu

    P.S. I hope you understand my english is a bit rusty
     
  19. Filth

    Filth Active Member

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    so, its 100% safe? what happens if one of the PSUs becomes unstable for no reason?
     
  20. Andrull

    Andrull Member Guru

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    I woud doubt it will make any harm to the rest of your komponents if one psu got unstable, becouse i can ripp out the power cord (230/115v) from one psu, and the other one just standing there blinking inn evry neon light conected and the fans start to spinn slowly. And this doesn't make any harm to my pc. And i Seriously doubt that a unstable psu woud do any more harm.

    If one psu is too unstabel, and shut down, the other one shut's down too. Becouse the on/off funksjon is connected togheter, and you cant turn one off and have the other one ON at the same time. (only if you unplugg the power cord).
     

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