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Mid 2012 model, A1278 / 2.5 GHz i5 or 2.9 GHz i7 processor.

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White Screen out of nowhere...?

Clean Installed Catalina and system boots and we can hear it talking Mac OS contains a built in whatever blah blah...... (Set up Menu voice prompt)..... And we can see the display slightly dim down after some 10-20 seconds or so which is normal, BUT there is no picture just a white display. It was working fine earlier today...... I haven't tried an external display as the owner will never use one anyway,...I have reset the PRAM & SMC, cleaned the display connector both ends, and I cannot see any blown chip..... has the GPU decided to commit suicide on me? This is weird.

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Puan 1
6 Yorum

This model doesn't have a dedicated GPU. Did you clean and repaste the CPU's TIM? You may have been too generous with the TIM.

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@danj I never did anything, thermal paste before yes, but earlier today and on numerous occasions before was booting OK with a picture etc..... just when someone comes to buy the %#*@ thing it decides to be funny.... :(

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@livfe - So... days ago you cleaned and repasted the CPU?

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@danj I repasted in maybe 6 months ago, then the unit has sat here waiting for a new home (Buyer)..... I has been tunred on and off 1-2x a month, and battery has always been with charge (Never run dry)..... It had a display this afternoon when I turned it on to show the buyer, shut it down, then 2-3 hours later the buyer came to get it, and we turn it on and welcomed by just a "white screen'....A PROPER WTF moment :(

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@livfe - The TIM migrated dirtying the small SMD devices on the green carrier board. Time to clean the paste off using an ultrasonic cleaner as the TIM often migrates under the SMD devices as well. You'll need to use a lot less paste as any spilling over the raw chip is what you need to prevent.

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@livfe ;-) check the voltage on L9004 on both sides of the inductor (L9004). You should get 3.3V on both sides. If the side to the LVDS connector is low, replace the inductor.

Block Image

Besides checking L9004 or after checking it, you want to check the LVDS clock lines. LVDS_IG_A_CLK_P pin 12 and LVDS_IG_A_CLK_N pin13.

Disconnect your power and your battery. Get your multimeter ant set it to Diode mode. Now place the Red probe form your meter to ground and use the Black probe on connector Pin 12 and then pin 13. Expectation is that you get a reading of 0.450 to 0.550 on each one of those. Any difference in that would indicate a faulty CPU

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Puan 2

6 Yorum:

@oldturkey03 Looks like you got it! Appears to be a small hole in the middle (Blown) 0.0V. Will replace this sometime today :)

I need you on a video call to assist me in fixing 3 or 4 A1466 MBA's & another A1278 (2012) :D

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@livfe good. That will definitely explain why you get a white screen :-) You can skip checking the clock lines :)

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@oldturkey03 We need 2-3 hours to confirm it was the cause 99% sure it must be, will try to add a picture of it in awhile.

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@livfe yes, absolutely. Take your time. No worries, there is no rush for anything on my end. I've been here for years and if everything works out I'll be a few more years :-)

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@oldturkey03 Apparently something to do with the LCD connector that has likely caused it to blow..... under investigation now, update in some hours.

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