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Resoldering the U8900-chip on the non retina MBP mid-2012?

Hey people, i have a Macbook Pro 15 mid-2012 (A1286), so non retina here. It has a black screen, external video works though, sometimes i even get video on the internal screen when i disable the 650M by software-mod but it's very inconsistent. For the retina-model there was a common problem that the U8900 chip needed resoldering. But i couldn't find much on the web for the A1286 model: Where is the U8900 on that board? Is it the same procedure as for the retina models?

Update (04/21/23)

Here are pictures: https://imgur.com/a/E1rUIbG. It shouldn't be the cable as it came with the new display assembly. The socket looks also fine to me...

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The unibody’s use LVDS signaling unlike the Retina models which depending on the series is either eDP or iDP.

I don’t have the schematics in front of me right now but I don’t think there is a comparable chip in this series.

I’m not sure why you disabled the discrete GPU (NVIDIA GeForce GT 650M). The 2011 models had the crappy AMD Radeon HD 6770M which just didn’t hold up for quite a few reasons. That’s not the say the NVIDIA didn’t have its issues but I rarely needed to deal with them and the approach of disabling the discrete GPU is different if it’s dead.

I’m suspecting you likely have a different issue at play here. Are you able to boot up in Target Disk Mode? Just press the T key just after you start the system. At which time you should see either a FireWire or Thunderbolt Icon on the screen. If you get that far you know the Iris graphics within the Intel CPU is working. If not that tells me the cable and or it’s connections between the logic board and the display need inspection and may need repairs.

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Thanks for your fast answer! I'll try booting up in target mode when i reassembled the machine. It is a really weird problem: sometimes i get display but no backlight, i only get backlight or i get no display at all. Weirdly with an external display display it works perfectly, which should mean that the GT 650M has no problem. Then again, forcing it to only use the GT 650M in display settings (turn graphics switching of) does not give me video on the internal display... I already replaced the whole display assembly to no avail.

The only situations where i got everything working:

1. Boot with external display, open gfxCardStatus, disconnect external display and then try to blindly click on "use HD4000". As one can imagine, it's literally "hit or miss", and as soon as i reboot, i have a black screen again...

2. Under High Sierra (didn't work under Catalina) disabling the GT 650M by that nvram-variable playing with the power preferences. But that worked very inconsistently :/

@jojojonjon - I’m really leaning at a bad cable or logic board connector as that often will effect both the data stream and the backlight.

Let’s get some nice detailed pictures of the cable end and socket area. So we can see the cables contacts and the logic boards solder connections. Post them here for us to see.

updated the original post with a link to pictures

@jojojonjon - The connector and cable on this side look quite good!

Sadly, there’s the other side 😟which need’s checking too! Follow this guide to pull the display assembly MacBook Pro 15" Unibody Mid 2012 Display Replacement then you can slide the black clutch cover for to inspect the connection on that side.

It shouldn't be the other side of the cable, the first thing i did was replacing the whole display assembly (cable included) with a non working one, it seemed like the obvious thing to do... Are there any other options i could try?

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