820-2915 Chimes but no Video only blackscreen

boxer

New member
Hello!
I got an 15" 2011 Hi Res, 820-2915 which chimes and boots into OSX but there is no video, just a black screen. Also on external I get no video.

What I did:

-PRAM & SMC reset (successful)
-tried another harddisc
-checked LVDS connector, supplies are there but LCD_PWR_EN does not enable U9000

-all power rails are there except:

PPVCCSA_S0_REG
only 0,9V
Checked U7100 (ISL95870A) and all components around, all ok. Regarding schematic, it should be 0,9V?! When VID0 and VID1 Voltage is 0, Output = 0.9V?!


PPVCORE_S0_AXG
0,9V but then falling down to 0,45V

PPVCORE_S0_CPU
1,15V but then falling down to 0,75V

I have checked current sensing circuit after the big coils on PHASE1,2,3,AVG and connection to U7400 (MAX17511). All ok.
That complete "PHASE" circuitry is a bit complicated to understand for me.....

Any ideas or hints how I should proceed or focus on??

THANKS
 
Last edited:

dukefawks

Administrator
Bad GPU, heat it up to 100C and try again. Was the GPU possibly already fucked with? Edge bonding still present?
 

boxer

New member
Ahhh... the plastic/silicin edge bonding is already missing... so it seems someone already tried ti heat it up. :mad:
So you mean, I should replace the whole gpu?
 

dukefawks

Administrator
So it was fucked with and it will at least need a new GPU. As these are nowhere to be found at the moment this project is a dead end for now.
 

dukefawks

Administrator
Yeah that will be a reball or a polished up fake or if you bought this 6 months ago it might have been the real deal
 

dukefawks

Administrator
Yes you can toss that in the garbage straight away. Why use someone else's reballed dead chip when you can use your own?
 

boxer

New member
Sorry, I am not fully into that GPU topic... whats wrong with refurbished or reballed GPU?! Dou you think that they just dont work?
I am afraid, that my GPU is completely dead... thats why I dont want to reball mine.
 

2andrewd

New member
Someone should correct me if I'm wrong but there were several years that had high failure rates to the point a class action lawsuit forced apples hand. For whatever reason those gpu's were all shit and since no one can buy direct from manufacturer the likelihood of a refurbished chip from those same years not failing is low
 

dukefawks

Administrator
The chip itself is bad, the problem is inside the chip. Heating it up will make it work for a few weeks.
Why do you think your "refurbished" chip was pulled from a board?
 

boxer

New member
Yes ok... but still I am wonderung, that my gpu us completely fucked up. I tried already to heat it up a bit to 160degrees... but still no change or image.
 

dukefawks

Administrator
I have no idea, only way to find out is to replace it. But replacing it with another zombie GPU is just a waste of time. Get a REAL NEW chip, they are out there, but very hard to find.
 
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