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Thread: Testing Opus 150 via ATX - Computer is Continually Rebooting

  1. #1
    Constant Bitrate long.1's Avatar
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    Testing Opus 150 via ATX - Computer is Continually Rebooting

    Hi All,

    I'm trying to test my Opus 150 Watt PSU via my 500 Watt ATX PSU via the instructions in:
    FAQ: How do I power my DC-DC PSU on my workbench? and Powering Your CarPC Outside of the Car.

    Whilst the Opus LED doesn't show any issues, the problem is that the computer is continually rebooting:
    1) I pull the switch to simulate ignition
    2) The computer turns on and goes through POST
    3) Windows XP starts to load - welcome screen displays
    4) The usual Windows load up sequence commences (wallpaper/icons displayed)
    5) Then Windows shuts down and automatically reboots

    At this point, all that is powered by the Opus 150 is the motherboard (Via Epia EN12000EG), and my 200GB Sata Hard Disk.

    I've searched for "Opus & Reboot" and found the following threads that seem to be similar, but nothing recent, and few potential answers:
    2005 - OPUS keeps Rebooting my system
    2005 - Just got my opus
    2004 - weird rebooting problem..possibly power related..
    2004 - Opus in eternal reboot

    So I've used my multimeter and taken some photos, and here's what I've found:

    ATX Power Specs


    Connecting Pins 13 & 14 on ATX power connector


    Switch to Simulate Car Ignition


    Voltage coming out of Opus molex (PC on)


    Voltage coming out of ATX molex (PC on)


    Voltage coming out of ATX molex (PC off)


    Based on this, and my research in the other threads, it might be that there's not enough power coming from the ATX PSU. I'm not sure why/how this is the case ? Also, if the Opus is smart enough to shut down (to theoretically save the battery), then I don't understand why it boots things up again straight away.

    For the record, when I connect up my DVD/CDRW and 2x headrest screens, the 10.5v figures shown above drops to about 10v, but the reboot issue still occurs at the same point during Windows initialization.

    So, either I'm doing something wrong, don't understand the concepts well enough, or I desperately need some electrical advice. Perhaps it's all of the above. Either way, I will welcome any of your thoughts/comments.

    Cheers,

    Long.1

  2. #2
    Maximum Bitrate psyrex's Avatar
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    Well, if the input is 10.5v to the opus, then it shuts down. The load removed, voltage goes up to 11.33, and (since "ignition" is still on) the opus restarts.

    You should probably measure the amps going into the opus just to be safe. I had a similar problem where a bench supply I was using was supposed to give 11A on 12V, but as soon as I had even 3A on it, the rail drops to about 10v. Just try a different power supply.

  3. #3
    Constant Bitrate long.1's Avatar
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    Quote Originally Posted by psyrex View Post
    Well, if the input is 10.5v to the opus, then it shuts down. The load removed, voltage goes up to 11.33, and (since "ignition" is still on) the opus restarts.

    You should probably measure the amps going into the opus just to be safe. I had a similar problem where a bench supply I was using was supposed to give 11A on 12V, but as soon as I had even 3A on it, the rail drops to about 10v. Just try a different power supply.
    Thanks for that psyrex - much appreciated.

    Your explanation of the opus rebooting makes perfect sense - thanks. I was struggling to get my head around that one. I thought that my "smart" opus was acting "dumb", but as it turns out (in this testing scenario) it's too smart for its own good.

    As you can probably tell, I'm new to the numerous functions of the multimeter. I'm doing some research into measuring amps, and have found a useful flash tutorial here. Now to convince myself that I know what I'm doing where the PC/PSU is concerned.

    Lastly, I'll also see if I can dig up another PSU somewhere. Might be lucky. Thanks again.

    Cheers,

    Long.1

  4. #4
    Constant Bitrate long.1's Avatar
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    Ok, I've managed to locate an old 200 Watt Power Supply, but it's an AT motherboard PSU not an ATX PSU.
    The Pinouts are detailed here: AT motherboard power supply pinout.
    So, the 3 questions I have now are:

    1) Can I use this AT PSU for my Opus testing ?
    2) If so, do I need to short two pins like pin 13 and 14 on the ATX PSU ?
    and
    3) If so, which pins do I short ?

    Cheers,

    Long.1

  5. #5
    Maximum Bitrate psyrex's Avatar
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    AT boards have a physical switch. There should be a label on the PSU showing which needs to be connected. It's usually 4 wires (could be 2, I guess) on it's own bundle (not the on the same bundle or wires for the motherboard or disk drives).

    Make sure there's enough amps on the 12v rail. There's usually not as much amps on 12v available on AT power supplies.

  6. #6
    Constant Bitrate long.1's Avatar
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    Quote Originally Posted by psyrex View Post
    AT boards have a physical switch. There should be a label on the PSU showing which needs to be connected. It's usually 4 wires (could be 2, I guess) on it's own bundle (not the on the same bundle or wires for the motherboard or disk drives). Make sure there's enough amps on the 12v rail. There's usually not as much amps on 12v available on AT power supplies.
    Thanks for all your help psyrex - much appreciated.

    I've checked the AT power supply and much of what you've stated above rings true. First of all, there's no fuse/output ratings on the sticker like on the ATX supply, so I have no idea if the amps will be sufficient or not. It does have a series of diagrams (shown below) which mean little to me, but I know enough to realize that it's referring to the four wires leading to the power switch (just as you suggested).

    I've tried to show all that in the next photo. I've also included the two-pin connector that is coming out of the 5v of one of the AT's molex connectors. See below:



    So I guess the question remains, is it possible to fool this AT power supply into thinking it's connected to a motherboard ? If so, which wires need to be shorted ?

    Cheers,

    Long.1

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    Low Bitrate MibMib's Avatar
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    Oh ! as i understand - you didn't load +5v rail of 500w atx psu. So there is cross-regulation feedback loop inside 500w atx psu- here is your problem, if one of 5 or 12 v rails isn't loaded enough - voltage on high-loaded rail drops. To fix this bug all you need is to load 5v rail(red wire) by using 1 or 2 12v 21W automotive lamps( try 1 if it's not enough - connect 2-nd in parallel) - 12v rail will take high value. Very simple sollution.
    400Watt CarPC power supply for powerfull systems- thaks for Beta testers- it was perfect.

    Remember - AMD Athlon XP (socket A) powers from 5v rail in most times !

  8. #8
    Constant Bitrate long.1's Avatar
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    Quote Originally Posted by MibMib View Post
    Oh ! as i understand - you didn't load +5v rail of 500w atx psu. So there is cross-regulation feedback loop inside 500w atx psu- here is your problem, if one of 5 or 12 v rails isn't loaded enough - voltage on high-loaded rail drops. To fix this bug all you need is to load 5v rail(red wire) by using 1 or 2 12v 21W automotive lamps( try 1 if it's not enough - connect 2-nd in parallel) - 12v rail will take high value. Very simple sollution.
    Thanks MibMib,

    I appreciate your input here, and it's definitely worth a try before swapping everything over to the AT power supply. Most of what you've said makes sense, and yet some of it puzzles me. I have a globe (pictured below) that says its 12V 55watts. Could I use this ? Also, are you suggesting that I connect it to the 5V Rail (Red) even though it says its 12V ? And lastly, as you can hopefully see below, it has only one blade connector. Does it not need to be grounded to the black wire as well ?



    Appreciate yours/others feedback.

    Cheers,

    Long.1

  9. #9
    Low Bitrate MibMib's Avatar
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    I have a globe (pictured below) that says its 12V 55watts. Could I use this ?
    Not sure , but I think you couldn't use it. This lamp in cold state has a very low resistance and it will overload atx psu at first time - i think internal overload protection will turn off yours atx psu in best way.
    So simply use small 21w lamps like in rear stop signal on old cars, try 1 - if it's not enough - 2 in parallel.

    Also, are you suggesting that I connect it to the 5V Rail (Red) even though it says its 12V ?
    Yes, you must connect it to the 5v rail ( red). Simply 12 v lamp which powered from 5v will lights with smaller brightness- don't worry about this.

    And lastly, as you can hopefully see below, it has only one blade connector. Does it not need to be grounded to the black wire as well ?
    Any simple lamp has 2 contacts for powering.
    As you can see - this wire in car connected to +12v through car wiring and electronics. Also we needs ground( chassis) connected to outer iron contact of lamp to power it . So you must ground outer iron contact of lamp.

    The best way , as i wrote, to use 1-2pcs 12v 21w lamp, but i think you will need to solder wires to contacts of this lamps or use special car lamp holders - i think you can find it in local autoparts shop.
    good luck
    400Watt CarPC power supply for powerfull systems- thaks for Beta testers- it was perfect.

    Remember - AMD Athlon XP (socket A) powers from 5v rail in most times !

  10. #10
    Constant Bitrate long.1's Avatar
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    Thanks MibMib,

    Following on from your advice, I decided to have another crack at the simulation via the 500W ATX before I sack it altogether. So I wired everything up again for another attempt - I'm much faster at it 2nd time round. I decided to follow a subsequent post by cliffloehr in the FAQ, by shorting pins 8 and 9 on the ATX. To my surprise, the PC booted up fine and did not auto shutdown.

    So naturally I decided to do some more testing. Basically, my reboot issue is more intermittent now as opposed to continual. Sometimes the PC will auto reboot during the Windows startup, and sometimes it just stays on, and the PC can be used as normal/expected. I removed the short of pins 8 and 9 in my testing and found that this made no difference. So I figure now that somehow my wiring/connections must have improved from my first attempt - not that I noticeably did anything different. So when the PC is on and booted OK, I test the 12v reading from the ATX molex and once again it's below 10.5V.

    In any case, I'm "reasonably" happy with that for now, as my primary goal was simply to test that the Opus 150 Watt PSU actually worked. Noteably, when I turn off my "simulated ignition" switch, the PC doesn't shut down. There's no jumpers installed, so I would have expected a 10 second delay before PC shut down. I guess I can concentrate on this a little more when I move to testing in the car. I'll hunt around for some relevant threads as well.

    As far as the lamps go, thanks for your valuable info MibMib. I'll definitely pick up a couple of these from my local JayCar store. I'll be there soon looking for a heap of other stuff for my install. Once I've got the lamps, I'll give them a go, and report back in this thread.

    Thanks for all your help.

    Cheers,

    Long.1

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