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Thread: Computer turning off during boot (Opus 150W with +5v&PSON mod)

  1. #1
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    Computer turning off during boot (Opus 150W with +5v&PSON mod)

    So a while ago I was having problems with my usb devices staying powered, and draining the battery. At that time I read through the very lengthy thread, and found rando's schematic. I grabbed a DPDT relay, some diodes, and implemented the mod. Things worked great for months like that. Recently I had the computer out of the car for a few weeks, and after putting it back in I'm having problems. Basically the system starts up as expected but just after POST it will turn off; the power will be cut, and the Opus will go into it's standy-by green blinking light phase.

    Setup:
    Opus 150W
    iBase MB870 with 2.6 celeron
    most other devices disconnected (so I know it's not a power draw issue)

    Mods (related):
    Rando's DPDT (to turn off +5 standy power to usb devices)
    Have case power switch and opus switch wired in parallel.

    A few weird things.
    First, this used to work fine; none of the wiring was changed.
    Second, if during the boot sequence I restart the machine (using the case power button), then the restarted boot sequence will load the machine fine. The only issue in that case is that the opus won't shutdown the computer when it has been restarted in this manner.
    Third, the bios is set to not restart on power failure. But if I disconnect the power switch lead from the motherboard, the machine will still attempt to start like normal. Could Rando's relay mod be turning the machine on?

    Anyway, I've verified all of the wiring is correct, and the relay is being fired appropriately, so I'm now at a loss.

    Any ideas?

    Thanks

  2. #2
    Variable Bitrate DaveB's Avatar
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    Try re-seating the RAM. I've seen PCs do what you describe when the RAM's contacts aren't clean or are not seated properly. If that doesn't do it, then disconnect everything and reboot, each time adding one device/cable back into the mix, until you discover what is causing the problem.

    I also ran into a problem like you describe when I had the power for my USB DVD drive wired up with the center of the power plug wired for positive. Turns out it needed center negative.

    You'll figure it out via the process of elimination. Good luck.
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  3. #3
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    I think the power supply might have some problems. I tried the RAM thing, just out of curiosity, although it didn't seem to matter. Also, there wasn't anything else to remove (I had already removed all devices, etc) from the system.

    I change the cable I was using between the motherboard and the power supply although this didn't seem to change anything. So that means it's most likely not the +5v usb power mod.

    The odd thing is that even with the power switch cable removed from the power supply, and the ACC line not connected the machine will power up the second the power is turned on. Since the only thing that could turn on the motherboard (or off) would be the power supply, that's what i'm left with.

    Has anyone else had a problem like this with the opus? I even have the case of the powersupply removed incase of components touching it. I guess I should write to Opus, but thought i'd check here first.

    Thanks

  4. #4
    Variable Bitrate DaveB's Avatar
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    Here is a long-shot for you. Is there a wire from the power supply to the pins on the motherboard where you would normally hook up the power on/off switch? If so, try reversing the wires (swap the connector 180 degrees).

    Those damn connectors are polarity sensitive. You would not think so -- with it being a switch. But they are. The sensitivity to the polarity comes from the attachment to the power supply. If it was configured normally to a switch on the case then I don't believe that the polarity matters. I don't have an Opus so I'm not entirely sure what you are dealing with. But on my M2-ATX that power switch connector gave me all kinds of grief until I figured out the polarity issue.
    8" Lilli TS
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    ENGENIUS WiFi MINI-PCI CARD 802.11A B 400MW OUT
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  5. #5
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    Tried that a while ago, as I realize the polarity of the wires matters to the power supplies (although it doesn't to the case switch, which is just a simple short).

    Thanks for the suggestion, but as I mentioned above, the problem still occurs (and the machine attempts to boot) with that cable removed.

    I've attached another power supply (non dc-dc), and the machine functions as normal, so I'm pretty sure the 150W is the problem. I've written Opus, and hopefully will hear from them soon.

  6. #6
    Variable Bitrate DaveB's Avatar
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    I agree...it has to be the power supply. The PC should not boot with the switch wire removed.
    8" Lilli TS
    MB896F Mini-ITX MB
    2GHZ Dothan 533MHz FSB CPU
    1GB SDRAM DDR2 533
    Seagate 300GB SATA150 HD
    ENGENIUS WiFi MINI-PCI CARD 802.11A B 400MW OUT
    Pioneer Slot Load SLIM DVDRW
    Bluetooth V2 USB 2 Dongle
    3COM BKP Cam

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