Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor

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How can I test the Power Supply 310 W LiteOn (voltage values)?

How can I test the Power Supply or Backlight Board (voltage values)?

Power Supply 310 W (661-5972) (LiteOn)

Backlight Board 661-5980

Model: iMac 27" - Mid 2011 - 3.1 Ghz

AMD Radeon HD 6970 1Gb.

Black screen, no power beep, fans spin, cd drive sound, no led keyboards.

Board Leds Behavior:

led 1: on

led2: on

led 3:off

led 4:off

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Although it is very probably that the videocard is the person in charge of the blackout, really I would like to discard any flaw in the Power Supply and the Backlight Board.

For it it would be useful to measure the voltages

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Deck the Halls
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1 Answer

Chosen Solution

This sounds like a GPU issue which is well known on this model. To test, hook up an external monitor.

Apple did do recall for these models but it has now expired:

The problems have been documented over the past couple of years on Apple’s own Support Forums.

Additionally, the iMacs must fall in the following serial number configurations:

The last four characters of the serial number must contain one of the following groups (for example, xxxxxxxxDHJQ):

DHJQ, DHJW, DL8Q, DNGH, DNJ9, or DMW8

DPM1, DPM2, DPNV, DNY0, DRVP, DY6F, F610

Here's more info on it: https://9to5mac.com/2013/08/16/apple-ope...

A hot air station reflow of the GPU card has been effective as a fix.

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(A hot air station reflow of the GPU card has been effective as a fix.)

OK. Would a dryer of powerful hair work?

By how much time would heat be applied to the GPU?

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No a hair dryer won't cut it.

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Here is just to reiterated what @mayer is already guiding you to:

LED Startup Sequence

LED #1 = Power available.

If no LED is visible:

• First disconnect the power cord from computer, then reconnect it to reset the LED

status, in case computer was correctly shutdown and AC was kept connected since

• Verify AC source

• Verify known-good power cord is connected

• Verify cable connection between AC inlet and power supply

• Verify cable connection between power supply and logic board

• Verify power supply

LED #1 + LED #2 = Power available, and system is powered on.

If second LED is not visible when power button is pressed:

• Verify power button connection to logic board

• Verify power button functionality

• Verify cable connection between power supply and logic board

• Verify power supply

• Verify logic board

LED #1 + LED #2 + LED #3 = Power available, system is powered on, and video card found.

If third LED is not visible after power on:

• Verify that the MXM video card is seated properly

• Verify if boot chime is present and fans are running when powered ON (reset SMC and

PRAM, reseat or check backup battery if necessary for proper boot up):

If POST boot chime is not heard, go to No Startup symptom flow,

If POST boot chime is heard, go to No Video symptom flow.

LED #1 + LED #2 + LED #3 + LED #4 = Power available, system is powered on, video card

found, and internal LCD found.

'''If fourth LED is not visible after power on:

• Verify internal DisplayPort cable connections between LCD panel and logic board

• Inspect LCD display cables for cable damage

• Verify external video functionality, and according to result check the following items:

If external display works then verify/replace the LED backlight board

If external display works then verify/replace the LCD panel

If external display does not work verify/replace the logic board'''

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The computer goes a damaged month, but 2 weeks ago,

I started the computer and there was no changes (not screen, fans activity)

and I forgot the matter for a few hours,

when I returned the fans they were to full and the computer was alive again,

it started normally, worked 2 days and later it went out again.

I have tried to repeat this event without success.

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