Question about some mobos not using -5V white wire...

By Vigilante
Oct 1, 2005
  1. Hey, it's common, I've seen, that HPs and other OEM PCs have power supplies that are missing the white wire on the 20-pin plug. This is the -5V line.
    If you plug a power supply into the mobo which has the white wire connected, it can hurt the mobo and/or the power supply. I've run across this multiple times.

    But now I want to know, is there a way to tell if a motherboard uses or doesn't use the -5v? I tried doing some googling, but that doesn't get anywhere. And I supposed I'd have to track down a schematic or some such. Is there any simpler way to tell?

    I just don't understand it. If a motherboard or power supply, does or does not use the -5v, and if damage can occure depending on which, why is this information not slapped on them with a big warning sticker? And why don't power supply makers and motherboard makers inform people about this?

    Case in point: I've got a system here that is an E-Machine. I don't know the history of it. But it had blown a power supply and the owners bought a new one. Now I have it, and the new PS does not have a white wire on it. Even though it is an Antec SmartPower 350W power supply. Which looks retail and not oem from E-machines. However, I can't be sure if the E-Machine motherboard uses or doesn't use the -5v. The motherboard is an ECS L7VMM2. Which doesn't look OEM to me either.
    So I said screw it and tried my own test power supply with and without the white wire connected. No luck, still doesn't POST.

    I'm saying the motherboard is dead. Because his other parts test fine, including the CPU. But the question is then, did the motherboard fry because the power supply didn't have the -5?

    So anyways, this -5 white wire issue comes up all the time here. We have had many cases where we just snip the white wire to put a standard PS in someone's PC, which works fine. But how can we be sure whether a motherboard uses or doesn't use it?

    Any thoughts?
  2. Tedster

    Tedster Techspot old timer..... Posts: 6,000   +15

    many of those PCs you mentioned use proprietary architecture. HP, Dell, etc.... generic parts often will not work as substitutes or replacements....

    after market power supplies are designed for generic systems.
  3. Vigilante

    Vigilante TechSpot Paladin Topic Starter Posts: 1,666

    Tell me about it. One of the big reasons to buy a custom.

    But still, should somebody, unknowingly, plug a generic PS into a mobo, not knowing the -5v should be snipped, will toast the PS. This can be the case obvioulsy if somebody has just the motherboard or in other ways doesn't know it was an OEM.
    And then, of course, not ALL OEMs have the -5 removed. It just comes up on a case by case basis.

    It gets even worse with some older Dells, who even rewired the 20-pin plug for their mobos. Now why in the name of all that's standard would they rewire a standardized power supply plug! It serves utterly no purpose except to screw people over. But y'all can buy Dell if you want..[/rant]
  4. Tedster

    Tedster Techspot old timer..... Posts: 6,000   +15

    I would never buy a Dell - other than good looks, they're piss poor computers. I haven't liked them since 1990!
  5. Vigilante

    Vigilante TechSpot Paladin Topic Starter Posts: 1,666

    sing it brother!
  6. Tedster

    Tedster Techspot old timer..... Posts: 6,000   +15

    la la la, mi mi mi mi!

    (am I in the right key?)
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