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Thread: Uh...I thought 2.5" are easier to power than 3.5" HD's (M2-ATX)

  1. #1
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    Uh...I thought 2.5" are easier to power than 3.5" HD's (M2-ATX)

    Ok well I have no answer for this but maybe somebody else does.

    So I built a nice little platform over the weeked that I mounted my 2.5 HD and M2-ATX to thinking that everything was going well. After I hooked it all up to my mother board (Biostar M7NCG w/ XP-M 35w) not a whole lot happened. Since I didn't have it set up for "Boot on power loss" I was forced to use a switch. Funny thing is everytime I pushed it the CPU fan moved then stopped. So I decided to unplug the 2.5 HD I was using (connected via an adapter). Well once it was removed the board booted up fine. I did notice in my BIOS that the 5v rail didn't have much if any output (hence no 2.5 boot). Well I plugged in a 3.5 HD out of curiosity and it started up fine! I'm assuming this might be a somewhat common problem but I haven't been able to find any posts of anybody having this issue with their HD's specifically.

    Does anybody have any suggestions?

  2. #2
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    what adapter you using? Sounds like maybe there is a problem there... I'm not super familiar with 3.5 to 2.5 adapters, but it has to inject power somehow cause 2.5's don't have a molex in conservation of space, and regular eide doesn't supply enough voltage to spin up a drive.

  3. #3
    Maximum Bitrate JimmyFitz's Avatar
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    Your 3.5" drive probably runs from the 12V rail whereas the lappy drive runs from the 5V rail. When the PS tries to startup while overloaded, it detects that it isn't working right and shuts down. USB devices add to the 5V load too.
    ~Jimmy

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    So I'm guessing that there isn't enough power on the 5v rail? The M2-ATX is suppossed to be putting out 40 watts (5vx8A). I hardly doubt that the little 2.5" HD is taking up that much power. Is it possibly a problem where my mobo isn't booting b/c it can't detect any power consumption on the 12v rail, but it can pick up the IDE cable? So a power "mismatch."

    Right now the adapter only has two wires for power coming out of it (a red one - 5v and a black one - ground). I know I should have thought of this sooner but should I take the yellow wire that isn't being used and solder it back into the yellow wire in the main harness? That way it tricks the mobo into thinking it is giving a signal to the HD?

    Thanks for your feedback thus far!

  5. #5
    Variable Bitrate nkotch's Avatar
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    So, from the 2.5" HD adapter, there are only the two power wires connected to that molex? (red, and black) or does it have all 4 wires on it?
    Nick
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  6. #6
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    Other then current draw... the mobo can't "know" that its sending a signal to a device over a power wire. Not sure if your mobo monitors current draw, but I wouldn't imagine that they would have built it to not boot if you didn't have a hard drive... what if you didn't want a hard drive for some custom reaason.... mobo's tend to do the boot for half second then shut down thing for a failure or protect reason like too much power drawn or direct short, or processor missing, but not cause it doesn't sense current drawn from the 12v rail.

    I still think its something crazy with that adapter... try maybe the adapter in a different machine.

  7. #7
    Variable Bitrate nadir_s's Avatar
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    make sure you've installed hte 2.5" adapter correctly on the laptop drive (by pin #) .. and make sure the you have hte - / + correct for power to the adapter.

    Well, if you didn't do it right the first time, the adapter usually burns out (been there ...)
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  8. #8
    Constant Bitrate Specimen's Avatar
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    JimmyFitz, your right about the 2.5 only needing the 5V, and the 3.5 needs both the 12V and the 5V. Since you don’t need 12V, there should only be 2 power wires. So if you’re not putting out 5V on that rail like you said, then there is something wrong.

    Check to make sure the cable's pin numbers are matched up like nadir said. 2.5 hard drives usually have a 20 key (no pin at 20) to prevent the user from flipping the connectors. Unfortunately, 2.5 to 3.5 adapters don't always have the 20 pin Key filled in so it's easy to mismatch the pins. If your adaptor doesn’t have that key filled in, make sure you have all 44 pins connected and that you didn’t accidentally offset the pin connections to the side so that two pins aren’t connected. If you do this you run a risk of running 5V straight to gnd.

    For god’s sake don’t be soldering anything to anything. These adapters and cables are all made to be plug in play and don’t need to be modified. You don’t need to trick the mobo, it will sense the HD through the IDE and not through the power consumption.

    Also what is your jumper setting for the J10 (A,B,C,D)? If you could post a pick of the adaptor and how its all setup, that could help us out.
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  9. #9
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    just to confirm this is just a wrong adapter or one that isn't getting proper power.... I've been through this exact same problem. I used a different adapter that looked pretty much the same, but it fixed it.

    once you have the right adapter, feed it 5v directly from the power supply, it should spin up just fine.

  10. #10
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    Quote Originally Posted by Vinister
    just to confirm this is just a wrong adapter or one that isn't getting proper power.... I've been through this exact same problem. I used a different adapter that looked pretty much the same, but it fixed it.

    once you have the right adapter, feed it 5v directly from the power supply, it should spin up just fine.
    I agree... been suspecting the adapter from the beginning.

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