iMac A1311 EMC 2389 mid2010

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  • ryogadan78
    iMac A1311 - Motherboard 820-3126-A, turn on sometimes
    by ryogadan78
    Hi guys, I have this 2011 iMac A1311 with a strange problem.

    Most of the time, when I plug in the power cord, the first of the 4 LED's turn on, but when I press the power switch the LED turns off and iMac won't boot up.
    Sometimes, when I unplug and plug the power cord back in, iMac starts up correctly by turning on the 4 LEDs in sequence.

    I have already tried a new power supply, but the result does not change. Do you have any suggestions?

    Motherboard 820-3126-A​
    04-06-2024, 05:19 AM
  • jasobrino
    trying to repair imac motherboard model A1311 (late 2009)
    by jasobrino
    Hello everyone,
    Some time ago I acquired an imac computer model A1311 that does not boot (motherboard ref. 820-2494-A).
    The power supply is working properly (I have two), it delivers the 12V on pin 4 of the power connector (PP12V_S5).
    As I have the schematic diagram and the boardview, I have made a series of measurements, obtaining the following results:

    PP12V_S5 -> 12V
    3V3REG_VCC -> 3.12V (something low?)
    PP5V_S5_LDO -> 0.02V
    3V3REG_VCC -> 0.0066V

    I have also measured the resistance to ground on the coils, and I can't find...
    02-20-2024, 11:48 AM
  • Crystaleyes
    iMac A1311 PSU repair questions
    by Crystaleyes
    Hi all.

    I have an ongoing issue with a 2010 A1311 21.5" iMac. It starts up, chimes, lights up and boots to the OS, however the screen starts to lightly flicker, steadily getting worse before switching off altogether. Measuring the voltages reveals that the 12v rail drops to around 10.5v once the Mac is switched on.

    Until yesterday, I wasn't sure if the problem lay with the PSU, the backlight inverter or the logic board.
    Yesterday, however, I borrowed a good PSU and the iMac works fine.

    Hence my opening a new thread within this troublshooting...
    07-04-2022, 04:50 PM
  • NConstantinou
    IMAC A1311 820-2784 BOARD NO DISPLAY
    by NConstantinou
    DEAR ALL
    i have the above board,, when i power on led604 does not come on. i do have PP3V3_S0, which goes across resistor R604.here i have again 3.3v,then does to led604. The lead of the LED that is connected to Q602 D-S i get 1.9v is that correct!
    on Gate which is MXM_GOOD i get 0v which is connected to PCH ic.
    is my problem the PCH IC!

    Thanks
    03-22-2025, 02:18 AM
  • dclass-pro
    iMac A1311 no USB port and displayport
    by dclass-pro
    Hi all guys, I received this imac in which the usb ports don't work, all of them and if I connect the displayport without the internal monitor, I have nothing on the video output.
    If I connect the original internal moditor, the imac turns on and works correctly and hangs on the login screen because the keyboard and mouse do not work to enter the password.
    I have 5v on the usb ports, in fact the led lights up on the mouse but it doesn't work. Do you have any advice?...
    03-27-2023, 08:37 AM
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