iMAC mid 2011 A1311 EMC2428

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  • fr0n1k
    Apple iMac A1311 Mid-2011 (820-3126-A) NO BOOT
    by fr0n1k
    Hello. Got an iMac after a power surge. The PSU survived, but the motherboard did not. Symptoms - after connecting the power, one LED (the rightmost one) lights up, 3.28-3.3v hangs on all legs of the bios flash drive, except for 4. The PCH is heated, low resistance PP3V3_S5 - 30 ohms, PP1V05_S0_PCH - 10-15 ohms. Powered through laboratory power supply 3V 1A to PP3V3_S5, the hub heats up wildly. USB data lines have the same resistance, not underestimated. There is no response to the power button.
    PP12V_S0 - 0.05V (should be 0), PP1V05_S0_PCH - 0.5V (should be 0)

    I've checked...
    10-22-2022, 04:10 AM
  • howardc64
    A1312 (27” iMac 2009-2011) A1407 (Thunderbolt Display) A1316 (Cinema Display) Display Black Screen Repair
    by howardc64
    Problem

    This is an LG edge LED lit LCD Display. The LEDs are on the bottom edge of the display. There are 2 bars (left and right) Each bar has many LEDs and a 6 pin connector. Each pin drive several LEDs thus is the highest current flow / heat junction. The weak lead free solder gradually fails with thermal expansion/contraction cycling and increases resistance. PSU will compensate up to a point, then when the current is too high, PSU just shut down the backlight causing a dark display. I have even seen one which the connector just fell off as solder points became completely detached....
    08-04-2024, 10:36 PM
  • Melania Ulibarrie
    iMac A1311 EMC 2389 mid2010
    by Melania Ulibarrie
    Hi, Need boardview and schematic of iMac A1311 EMC 2389 Mid2010
    04-16-2025, 09:03 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
  • SAFC
    imac 21.5 820-3126-A 2011 dont power on
    by SAFC
    The device was brought to me after self-cleaning. After replacing the thermal interfaces, the iMac stopped turning on. While the client was rummaging around in it, he touched the power supply with the processor radiator, after which there was a bang.

    I examined the power supply, replaced the burnt-out Zener diode ZD36 and the PWM controller DAP017. Now there are standby 12 and 4 volts

    When connecting the board to the power supply, autostart occurs, only LED 501 lights up. The cooler starts to rotate, after half a second it stops and so on in a circle. For these half a...
    09-21-2024, 05:20 AM
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