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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
Bu iyi bir soru mu?
İtibar: 685,2b
3,4b
1,1b
2,6b
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.
Bu yanıt yardımcı oldu mu?
(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?
No a hair dryer won't cut it.
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'''
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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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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