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  1. #1
    iMac A1225 EMC 2267 power supply (voltage, start)

    I would like some insights about iMac's power supplies, especially the Early 2009 24" (A1225 EMC 2267).

    I decided to tinker with an old broken iMac (machine that shuts itself down) to make it a Media Center with my Rasberry Pi and its Hifiberry + an LCD controller. But to do it right, I need to use the power supply for the screen (+ fan and why not also power the raspi).

    But for that, I need two things:

    • The voltages (and current) of the output connectors which are obviously not standard (12 pins for the 12v-3.3v and 12 pins for the 24v that runs towards the inverter of the screen, although for the latter, I don't really care).
    • Know which pins to connect to activate the power supply (if I had this element, I could measure the voltages myself).

    For now, I've spotted three things:
    • Pin 1 = Ground
    • Pin 2 = 12v always on
    • Pin 4 = 3.3v always on
    • Pin 6 = Ground

    For the rest, I'm drying up, if you'd give me a hand, I'd be extremely grateful.

    PS : Sorry for my pitiful English, I'm French
    Last edited by MrSoul; 09-07-2019 at 01:15 PM.

  2. #2
    iMac A1225 EMC 2267 power supply (voltage, start)
    chscag's Avatar
    Member Since
    Jan 23, 2008
    Keller, Texas
    Your Mac's Specs
    2017 27" iMac, 10.5" iPad Pro, iPhone 7+, iPhone 8, Numerous iPods, Mojave
    Rep Power
    Welcome to our forums.

    Your English is very good.

    As to the voltage measurements, unless someone here has access to the same equipment or even a service manual, we would be of no help to you. You might try going to iFixit: The Free Repair Manual and post there. Someone there who is tinkering around as you are may have some answers for you. Good luck with your project.

  3. #3
    Thank you, I also posted my question on ifixit!

    I have the equipment to make the measurements, the only thing that interests me is how to activate the power supply. (It must be necessary to make a bridge between two pins... but which ones?).

    PS: Unfortunately, the service manual only talks about diagnostics and parts replacement, nothing specific about power supply.

  4. #4
    iMac A1225 EMC 2267 power supply (voltage, start)
    krs's Avatar
    Member Since
    Sep 16, 2008
    Rep Power
    Activating that power supply may be more complex than you think.

    On the power supplies for the Mac laptops there is some initial communication between the chip in the magsafe connector and the Mac which then after about a second will cause the switching supply provide the full voltage -i's not just the bridging of some terminals.

    The power supply for the iMac powers up somewhat differently I would imagine, but don't assume it necessarily will be activated by only bridging two terminals.

    For the MacBook supplies, there is a very detailed technical description and analysis on line - have you search for something like that for the iMac supply?
    One thing to note is that diferent models (and years) of iMacs use different supplies, so you need to make sure you get the information on the one for your specific iMac.

    And finally - if the iMac you have shuts itself down, what makes you think that the power supply that you have is not defective and you can actually use it?

  5. #5

    Fortunately, the iMac's power system is simpler, they don't have to switch between the battery and a potential faulty or counterfeit charger.

    And no, unfortunately, I couldn't find any technical documentation on iMac power supplies of this generation
    If ever a reputable soul has good technical sources, the power supply is a Delta ADP-250AF B.

    Otherwise, I made some progress in my tests, I managed to activate the power supply!

    It is sufficient to make a bridge between the ground (PIN 1,6,7,12) and the 3.3V (PIN 4), which activates pins 8, 9, 10

    So we end up with these values:

    On the 12V output (2x6 pins)
    • Pin 1 = GND
    • Pin 2 = 12VDC -> Always On
    • Pin 3 = GND -> if SATA connected (creates a bridge with the last 1pin connector of the power supply)
    • Pin 4 = 3.3VDC -> Always On -> PS_ON
    • Pin 5 =?
    • Pin 6 = GND
    • Pin 7 = GND
    • Pin 8 = 12VDC -> If On
    • Pin 9 = 12VDC -> If On
    • Pin 10 = 12VDC -> If On
    • Pin 11 =?
    • Pin 12 = GND

    On the 24v output (1x12 pins)
    • Pin 1 = 24VDC -> Always On
    • Pin 2 = 24VDC -> Always On
    • Pin 3 = 24VDC -> Always On
    • Pin 4 = 24VDC -> Always On
    • Pin 5 = 24VDC -> Always On
    • Pin 6 = GND
    • Pin 7 = GND
    • Pin 8 = GND
    • Pin 9 = GND
    • Pin 10 = GND
    • Pin 11 =?
    • Pin 12 =?

    A last connector is present on the power supply, it is a ground that seems to be dedicated to the 5V (it is connected to one of the SATA GNDs and to the motherboard).

    We can see that this power supply only provides 12V and 24V, as surprising as it may seem, it is the motherboard that is in charge of transforming the 12V into 5V! (the cable between the power supply, the motherboard and the hard disk confirms it).

    So I still have Pin 5 and 11 on the 12V port and Pin 11 and 12 on the 24V port which are a mystery.
    Last edited by MrSoul; 09-08-2019 at 02:44 PM.

  6. #6
    I found the electrical schematic of a Liteon PE324101UN-LF power supply (which also seems to be used in other iMacs), there seems to be some info, but I can only guess the usefulness of these pins....

    On the 12V output (2x6 pins)
    • Pin 1 >>- +12V
    • Pin 2 >>- +12V
    • Pin 3 >>- +12V
    • Pin 4 >>- GND
    • Pin 5 >>- GND
    • Pin 6 >>- GND
    • Pin 7 >>- +5VS
    • Pin 8 >>- +5VS
    • Pin 9 >>- +5VS
    • Pin 10 <<<- AC_DET (Alternating Current Detection?)
    • Pin 11 <<<- P_DIM (Power DIMming?)
    • Pin 12 <<<- BL (LCD BackLight?)
    • Pin 12 <<<- PS_ON (PowerSupply ON !)

    On both 24v outputs (1x12 pins)
    • Pin 1 >>- 24V
    • Pin 2 >>- 24V
    • Pin 3 >>- 24V
    • Pin 4 >>- 24V
    • Pin 5 >>- 24V
    • Pin 6 >>- GND
    • Pin 7 >>- GND
    • Pin 8 >>- GND
    • Pin 9 >>- GND
    • Pin 10 >>- GND
    • Pin 11 <<<- P_DIM (Power DIMMING?)
    • Pin 12 <<<- BL_ON (BackLight ON?)

    For AC_DET, I found this definition:

    AC adapter voltage detection input. Valid AC adapter input range is set using resistors forming a voltage divider which are connected between ACDET & GND and ACDET & AC adapter.

    P_DIM should reduce the output power of the 24V PINs to reduce the brightness of the display?

    BL_ON, turn on the LCD?

    In short, full of new questions.

  7. #7
    Well, I finally succeeded in measuring everything I wanted.

    I made a little schematic for those who would be interested.

    If there's a mistake, don't hesitate to tell me.


  8. #8
    iMac A1225 EMC 2267 power supply (voltage, start)
    pigoo3's Avatar
    Member Since
    May 20, 2008
    Your Mac's Specs
    2011 17" MBP 2.2ghz, 16gig ram, OS 10.11.6
    Rep Power
    Thanks very much MrSoul for such detailed info & investigation!

    In case you didn't know...for the most part...the average Mac-User compared to the average Windows box not quite as much of a "tinkerer". If you take the subset of Mac-users that do tinker around with their computer...usually they do component replacement rather than component repair/troubleshooting. Of course there are some rare Mac-Users (like yourself) that would dig deep into things like you are.

    In other words in this particular case...the average Mac-User would probably either purchase a new or used power power supply & do the replacement...rather than try to get the original power supply to work. I'm sure many Windows box users might do the same as well. This is why you may not be getting quite as much help with this project.

    Lots & lots of expertise here...just not quite as much getting "Zombie" power supplies working again!

    - Nick
    - Too many "beachballs", read this: Beachballs
    - Computer seems slower than it used to? Read this for some slow computer tips: Speedup
    - Almost full hard drive? Some solutions. Out of Space
    - Apple Battery Info. Battery

  9. #9
    iMac A1225 EMC 2267 power supply (voltage, start)
    pm-r's Avatar
    Member Since
    Oct 16, 2010
    Brentwood Bay, BC, Canada
    Rep Power
    Lots & lots of expertise here...just not quite as much getting "Zombie" power supplies working again!

    Yeah... Apple's design switch away from the towers sort of put a halt to the old hacking and modding eh...??? At least in these parts of the Americas world.

    - Patrick

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