Molex 4 to Sata Power - Wrong Direction?


I recently bought a kit that can allow you to hook up a 3.5" drive to a usb on my laptop so I could work on it without it being in a computer.

Part of this kit obviously needs to supply power to the drive from the wall. The wall adapter provides a molex 4 connection, then a molex 4 to sata adapter if you have a sata drive like me.

I fried my drive with this and am very unhappy, but dont know if its what I did or if the psu is bad. I now see numbers on the molex 4 (1,2,3,4) on the different plugs, and see 1,2,3,4 on the adapter. I dont remember if they were not plugged in the right way when I did my drive, but the drive started smoking and never lived again.

Maybe I plugged them in the right way, maybe not. Would the wrong direction (4 with 1, 3 with 2, 2 with 3, and 1 with 4) kill my drive? I know the voltages on the molex 4 are different for each pin and that this could kill it.

Thoughts?? Ive looked on all of newegg's reviews for the adapter and no one seems to have made this kind of mistake. Is it just me that didnt consider this?? Or does it just not matter and the psu was just faulter and overkill.

Thanks for the help! I couldnt find anything on google that relates to direction mattering...
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  1. Best answer
    If you plug it in backward, all that should happen is you get +5v instead of +12v which would just cause the hard-drive to be underpowered. However, molex plugs should be polarized, so it wouldn't be possible to plug it in backwards in the first place.

    What adapter is it? How is the HDD "fried" though?
  2. The power supply might have been bad, low voltage usually will just cause things not to work, even if 12V and ground ended up switched you would just end up with reversed biased transistors doing nothing and a motor that spins backwards, it shouldnt have killed it. What might have killed it are either high voltage or very high ripple.
  3. Damn, then Im very angry at the manufacturer! I will test the power of the molex connector with my multimeter when I get some time, but Im angry that they cost me a $140 drive! (2TB WD green drive...brand new!)

    The HDD is fried because the first time I plugged it into the adapter, smoke started coming out. I IMMEDIATELY unplugged it and tried to let it cool off for a minute, but it smelled like it was burned.

    Tried plugging it into a working PC as a second HDD and it wouldnt spin up. Tried the adapter again which resulted in more smoke and a terrible smell. I am very sad about this drive, but am getting a replacement. Could the 12V rather than the 5V lead to too much current? (Current=Voltage/Resistance, more Voltage yields more current) that may have fried it?

    Timop, the adapter is the one in the link to ebay.

    Thanks for the help guys!
  4. Timop, if a molex, or molex like connector is involved, you are interchanging 5 and 12 volts. 12 volts into a digital board will fry it.
  5. I did notice that it IS polarized so I would have HAD to have had it in the right direction.

    I suppose this means that Im not an idiot and the damn power supply killed it. Thanks for the help guys!
  6. Is there any way to check if this power supply is bad? I looked at my multimeter yesterday and it looked like the voltages were okay. Could it be a bad converter from molex 4 to sata?
  7. jsc said:
    Timop, if a molex, or molex like connector is involved, you are interchanging 5 and 12 volts. 12 volts into a digital board will fry it.

    I believe most adapters runs only with 12V IIRC, AND HDDs prefer 12v over 5v also.
  8. Standard color code wiring for molex 4-pin power connector is:

    Pin 1 Yellow +12VDC
    Pin 2 Black Common Ground
    Pin 3 Black Common Ground
    Pin 4 Red +5VDC

    Serial ATA Power Connector, 15 Pin

    Pins 1, 2, 3 Not Connected +3.3VDC
    Pins 4, 5, 6 Black Common Ground
    Pins 7, 8, 9 Red +5VDC
    Pins 10, 11, 12 Black Common Ground
    Pins 13, 14, 15 Yellow +12VDC

    If your Molex to SATA power adapter cable is wired different to the above then that would explain the smoke.
  9. Best answer selected by ansemx324.
  10. I just smoked my HDD with a molex to sata power adapter.
    SOMEHOW the +12v and the +5v wires were swapped.
    I dont know was it some manufacturing error or someone
    played a bad joke on me... I dont remember from where did
    i get the adapter but is shure fucked up my hard drive.
    Fortunetly it was only a 80gb maxtor...
    So my advice, when ever you see a molex to SATA power adapter
  11. It doesn't necessarily have to be the adapter. I just recently bought a new PC, and the Molex cable/connectors were "cross wired." Click to see photo.

    The molex cable was connected to hot-swap boards that the drives plugged into. This cost me four brand new 4TB hard drives.

    I checked the cable connection to the power supply, but of course the connector is "keyed" so there is only one way to connect it.

    Can anyone think of a legitimate reason this would happen?
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