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820-2850-A GPU panic and green screen

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dukefawks

Administrator
The LVDS issue is the MUX U9600. They are pretty shitty to reball, so if you have little experience this is not recommended.
 
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sztomi90

New member
Thanks for the promt reply. I was suspecting that chip (that part needed the lightest touch for the screen to come back)...
I know you guys are agains reflowing but I was speculating that if I cannot reball that chip a reflow might be my only chance....what do you think? Would this have any risk?
What are the chances that I make it even worse?
 
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aprendiz

Moderator
Remove perfectly well all the glue around IC and go ahead with the reflow, if you don't have practice doing this, do it in a scrap board first....
 
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dukefawks

Administrator
We have to be real here, you have issues soldering C9560, I doubt a successful reflow of the MUX will happen. Bit of a shame to destroy a perfectly fixable machine.
 
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sztomi90

New member
Update:

Being desperate of not being to use my laptop I did find a fix: I folded a little piece of hard paper into like 1cm thickness and kapton taped it to the MUX chip then when I screw the case back on it applies enough pressure so that the chip makes pretty okay contact (sometimes if I hold in some ways it comes back sometimes but no big deal).

I know, I know it is kind of a lame solution but as Louis would say "Meh what do you want from me?" :P :D ;))

So I had been using the mac for two weeks like that. With the nvidia gpu turned on. It did work like a charm. Even the kernel panics dissapeard. That was kind of surprising to me. I was suspecting that contact issue with the MUX chip might had been contributed to the panics as well.....well anyway I was happy that it seem to work.

Then few days ago had a kernel panic again. (Also just after this upgraded to SSD with new osx). Panics still continued.....

The thing is:
That MUX chip reball seems way to complicated and risky to me now. Maybe in the future, when I will have more practice, and a good stencil for it I might attempt it. But till then the "paper solution" is fine for me....

My question is related to the kernel panics.
So if I got it correctly then it is NOT connected with the MUX chip issue, right? Is that problem ONLY caused by that cap (that I probably tortured to much when I put it on)? Cause if it is then I could change that again to a new one......(now doing things the proper way)

Thanks for the help again.
Cheers
 
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sztomi90

New member
Yes, I replaced it.

And since it did not solve the panics I started speculating why that might be. As I wrote in my first post when I measured after that rail with that cap it was 1.5v. The schematics, if I understand it correctly says is should be 1.8v.
So I was speculating that the cap might have been hurt a bit since it took a few attempts to get it flat on the board (repeated hot air rework can harm a cap maybe?)
or another thing that came to mind was that maybe some other component got hurt nearby......I have no idea what is the real issue.
 
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dukefawks

Administrator
Like a standard electrolytic cap in the form of a can? That will not work, need to replace with a 330uf from a scrap board, the black rectangular ones.
 
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