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ATX Wire Color Help

  1. Jan 26, 2010 #1
    I managed to pick up a few years old PSU from the computer science professor at college :D, If anyone remembers my post a few weeks ago I was very enthusiastic about this. However, I've identified all wires labeled and from the standard tutorials on the internet, the white wire typically listed -5V is the PG Signal and this PSU contained an external switch for the balling bearing fan. It is a Sparkle Power SG - 300G I tried finding a more detailed wire guide to help me clarify that at the very least the green wire is power_on for fact before I wasted my time and fry something I got for free. On the switch there was a o-ring terminal for the green wire and the switch 4 pole I believe I had White(PG) Blue(listed -5v) Brown(-12V) and Black(of course, GND) Thanks
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  3. Jan 27, 2010 #2


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  4. Jan 27, 2010 #3
    Yes, thanks I've read over several tutorial, through some googling for a few hours, I believe my PSU is maybe an AT, it has an external switch which turns the fan on and off with push push and by the switch is a terminal ring which is green, which I assume in very older motherboards was attached somewhere. The only voltages this thing can put out is 12 V and 5 V plus or minus, a white wire for Power Good Signal other werent defined such as brown, orange, gray, purple combinations used in 3.3 V for the corresponding color orange I believe. The unknown wires to me are brown the green terminal post which is connected to the DC Input outlet then that wire is grounded where another wire connected to the ground is ran through with the switch the switch having four posts white brown black blue, I am just trying to see if any if the unknowns correspond to a power on signal of the sorts so I can properly convert this PSU without wasting time and components

    The PSU: Sparkle Power Inc. SPI-300G 300 watt, I'd imagine very old

    This is the schematic of shorts for the exact PSU

    Found this in the link

    Power Good Signal: Power on delay time 100 ~ 500ms, off
    delay 1ms minimum (TTL and CMOS compatible)

    Does this mean Power Good is just a delayed Power On Signal function which I can use in my switch for my conversion?
    Last edited: Jan 27, 2010
  5. Jan 27, 2010 #4


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    Yup, that sounds like an AT supply (or more probably, an LPX--low profile baby-AT). It normally plugs into a 12(?) pin connector on an AT board:

    The green wire with the ring terminal is most likely a case or chassis ground and wired to the ground pin on the plug. Probably meant to go on one of the chassis screws.

    If I remember correctly, most of these had a switch on them which would directly connect the wall AC to the power supply. The memory's a little fuzzy on the particulars, but I think the back switch was wired to a remote switch on the front (that or a connection to drive an internal relay). Regardless, there was live 120/220 V on the switch. Post 3 (under the Power Switch heading) on the following thread goes into more detail about the wiring on the switch, which sounds like the part you're having difficulty with:
  6. Jan 27, 2010 #5
    I believe the next link on the page is it. The LPX Form Factor

    As for the green terminal it is grounded to the PSU case

    Thanks for the amazing help I am checking that link out now and will edit this post if need be, once again thanks!

    Exactly what I was looking for, however it doesnt seem like I can set up a remote toggle switch spst can i? and how would I wire the green terminal so the power comes on not just the fan?
    Last edited: Jan 27, 2010
  7. Jan 27, 2010 #6


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    I think you did the same thing I did--link to the frame, and not the actual page in question. Short of splicing longer wires on the switch, or maybe using a relay, or splicing an inline switch onto the power cord, there probably isn't a really easy way of making a simple remote switch.

    Lastly, the fan turning on should indicate that the power supply is also turned on and outputting power! The green terminal should have no impact on this.
  8. Jan 27, 2010 #7
    Id Imagine that the green wire has to be grounded to get power i ran a voltmeter on it and with the fan just on no output power i got from the 5v rail
  9. Jan 27, 2010 #8


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    No, the green wire should be the ground connection point FOR the case. This is meant purely as a protective measure, and should ordinarily never carry current. You shouldn't have to plug it into anything for the power supply to work. Wait, you're using the cable that was supplied with the power supply to connect it to the wall, right?

    If the fan is on, there should already be 5 or 12 V being generated (otherwise, the fan would not turn on--it's internally connected to one of the outputs of the power supply). The possibility is that one of the outputs has blown, and that might be why you don't see anything on that particular output. If it works only when the green wire is connected to ground, then you probably have a faulty connection somewhere inside the power supply (my guess: one of the connections to neutral is blown).
  10. Jan 27, 2010 #9
    Yeah the fan turns on, and the 5V rail measures 0.01 volts if that, but the fan is wired internally to a postive 12v rail ill test the 12 v rail
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