820-2915 no green light?

[Fizzl92]

I tryed a different DCIN board and still the same. But i just let it sit there plugged in and it seems as it will turn on every time if i just wait long enough. Than i can also see an apple (with no backlight - ill adress that when it works) on the screen and a normal picture on an external monitor. But it needs really long to turn the green light on. Can this be caused by the keyboard/Trackpad connector?

 

[aprendiz]

Check R7005, should be 20 ohm, check voltage on bothe pins should be about 16V...

 

[Fizzl92]

Both pins have 0,6V slowly going down when the light is off. Resistance is 23OHM. But after a minute or so it starts, chimes and the voltage is back up to 16V...

 

[dukefawks]

There should always be voltage on R7005. Measure voltage on pins of D7005

 

[Fizzl92]

I measured D7005 and it has 0,X V at all three pins slowly doing down. I followed PPDCIN_G3H back to F6905 anf there is also the same low voltage. But as it starts the voltage goes back up

 

[Fizzl92]

I noticed Q7080 getting hot and replaced it. I also corrected my jumper so that it is no longer connected to the case of Q7080 (i measured all connections of Q7080 and they conduct only to where they should (i also checked them the first time... maybe the Q7080 i took from a donor was slowly dying...)) and now it turns on every time. But Q7080 is still getting hot. On this machines the whole board is pretty hot so i guess that is normal for this model. I repaired the backlight and after that i noticed that it won´t boot up all the way. If i try to install an OS but it hangs after the apple disappears and it i want to boot from a drive with an OS installed. It also stops with a white screen after the apple finished loading. I tryed differend HDDs and HDD cables but still the same. Even without the HDD cable connected it won´t get to the installation menu. Now i am stuck again

 

[dukefawks]

Q7080 is getting hot because it is not being told to turn on. Check the trace to the gate R7081 and trace to the ISL.

It probably hangs during boot because the GPU is also fucked.

 

[Fizzl92]

I replaced R7081 and it seems to be cooler now. (but still nearly the whole board is warm/hot. I´m pretty sure i replaced or at least measured R7081 before because the trace to the gate was burned. The trace to the ISL is fine and the trace under Q7080 (pin 3) is my jumper and should be fine as far as i can measure. Is there a way to start it using just the integrated Intel GPU for testing? Is this the model where C9560 fails often?

 

[dukefawks]

Why don't you just measure the gate voltage? Heat up GPU to see if it boots again. No C9560 is on 2010 boards, not on 2915.

 

[Fizzl92]

Voltage to the Gate (PIN 1 of R7081) is 6,35V when turned on. Pin 1 of R7080 is 16V so i assume thats fine as Q7080 is a PMOS. I heated the GPU with my hot air until i couldnt touch it anymore but still the same. Should i heat it more? Also there is no visible issue on the picture. It just stays with a white screen after the apple finished loading

 

[dukefawks]

Hanging on a grey screen is 90% a GPU or VRAM issue. Heat up to 100C so a wet finger on the GPU sizzles. Also check for damaged components around GPU/VRAM. Is the original edge bonding glue still present?

 

[Fizzl92]

No Title

The edge bonding is still there. The only corrosion around the GPU was around ISL6263. There was one trace burned - i run a wire there. I attached a picture too. Should i replace the chip as well to be sure its good? I could not get it so boot up but i´ll try heating it more slowly.

 

[dukefawks]

So that means there was corrosion in GPU are. Could be corrosion under VRAM/GPU or corroded trace/resistor still in that area. It may be a good idea to replace that ISL and inspect all traces.

 

[Fizzl92]

I replaced the ISL and the first time the fans won´t spin anymore. I replaced it again and now its back to the grey screen. After that i heated the GPU again very much and (unfortunately) it decided to work again. So you were right again. Failing GPU... Thank you for the help. I learned a lot anyways

 

[dukefawks]

In reality every 2914/2915 board you will get that has not had the GPU replaced will need it. I cannot warranty these boards for any repair without putting a new GPU on it. So basically any liquid damaged 2914/15 are a write off if you want to provide a warranty on it.

 

[dukefawks]

GPUs are pretty much no where to be found. The ones you do find are 99% fake reballed garbage with 2016/2017 date codes put on them.