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Bzzzzzzt! Last modified: 02/10/13 03:00:47 PM
  FrankenMac
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    Wiring up a G4 mobo is almost painless. Apple conviently uses a 10 pin header with the same pinout across the G4 line up through the 'Quicksilver' machines. To power the machine up, you only need wire a momentary between pins 6 and 3. Most PC cases also have a reset switch, use it as such by wiring it to pins 8 and 3, or use it as a sleep button by going to pins 4 and 3. (The one obnoxious part of this setup, Apple used a common ground, so all switches/LEDs have one leg wired to pin 3.) Simple, right?

    The Power LED is a bit more of a pain as you can't just wire it directly. Instead, you need a transistor, fed power from pin 7 which is hot whenever the system has power. The transistor is signaled by pin 1, and sends its output to the transistor. This is the writeup I used to set my 'throbber' LED up. To do things properly, you're going to need a soldering iron, a 10 pin ribbon cable and plug, heat shrink tubing, a transistor and resistors, wire posts, and possibly a case or other enclosure. To do things ghetto, scotch tape and a lack of patience are all thats required.

     
      12  
      34  
      56  
      78  
      910  
     
    1  - Status +0.5v 
    2  - Unknown 
    3  - Common Ground
    4  - Sleep
    5  - Unknown
    6  - Power
    7  - +5v 
    8  - Reset
    9  - Unknown
    10 - Programmer's Switch
      
    Extra credit for noticing Serial Port headers use a 10 pin cable and plug that is a perfect fit...


    The internal speaker header is usually right by the front panel board header. It's a two pin connector similar to PC cpu fan headers. This on is simple, two wires, one speaker.

    For those who've heard rumors that you can use a PC ATX power supply to power your G4, they are true. Depending on the motherboard you go with, you may be in for alot of extra work. I will restate one more time, if you don't like soldering and risking hundreds of dollars worth of hardware to an oopsie, get an Apple power supply that matches your system. 'Yikes' and 'Sawtooth' systems can use a PC power supply with a two wire mod. 'Gigabit' and later systems require +28v feeds, which PC power supplies do not provide. You can get around the 28v problem using an extra wallwart power supply.

    PC ATX Yikes/Sawtooth Gigabit/DigitalAudio Quicksilver Mirror Drive Door
         
               +5vSBGND  
             GND+28v    GND+28v    GND+28v  
     +12v+5v    +12v+5v    +12v+5v    +12v+5v    +5v+5v  
     +5vSB+5v    +5vSB+5v    NC+5v    +28v+5v    +5vGND  
     PG-5v    +3.3vGND    +3.3vGND    +3.3vGND    GND+3.3v  
     GNDGND    GNDGND    GNDGND    GNDGND    +3.3v+3.3v  
     +5vGND     +5vGND     +5vGND     +5vGND     GND+3.3v   
     GNDGND     GNDGND     GNDGND     GNDGND     -12vGND   
     +5v
    PWR
    ON
        +5v
    PWR
    ON
        +5v
    PWR
    ON
        +5v
    PWR
    ON
        GND+12v  
     GNDGND    GNDGND    GNDGND    GNDGND    +12v+12v  
     +3.3v-12v    +3.3v-12v    +3.3v-12v    +3.3v-12v    
    PWR
    ON
    GND  
     +3.3v+3.3v    +3.3v+3.3v    +3.3v+3.3v    +3.3v+3.3v    GND+12v  
                       


    Note, the colors used above are not universal. Use a meter to verify your power supply puts out voltages you expect where you expect it. You will need to take your power supply of choice and rewire it to match the system you want to use it on. The easiest method is to get a PC ATX power cable extender if using a 'Yikes' or 'Sawtooth' machine, or a PC ATX to EPS12 adapter for others. You can then make your changes to the adapter's wiring, leaving your chosen power supply bone stock. Even though the EPS12 connector is 24 pins, it will fit a 22pin connector. The connectors are keyed, so you can't goof the layout unless you like using excessive force.

    The 28v feed is really approx 24v, and can be provided by an external power supply like a wallwart. For a clean setup, use an old blank slot cover as a mount point for a barrel style power jack. Run the lines from that to your adapter harness. You then plug the wallwart into the slot cover and viola, a PC power supply operated Power Mac.

    Be smart, triple check your work, and if you are unsure, stop, and seek assistance. Mis-wiring a power supply can wreck a project very quickly, and cost you ALOT more than you would have spent buying a matching Apple power supply. While I'm running a cheapo unregulated wall wart for 28v, I recomend a regulated unit. The 28v feed operates some of the power management sections of the motherboard. A surge or undervoltage event can result in random locks, or a system that won't power up. You have been warned.

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