820-2915-B, chimes but no display

[rookieme]

I have faced up some issues with the specific board from MacBook 2011 with either the 216-0810005 or 216-0809000.
They usually don't boot at OS or display lines at display so I replace the GPUs and they usually work.
Recently after replacing the GPU [216-0810005] the macBook boots, chimes but shows no display at both Internal and external display.
Same issue today with one with 216-0809000 gpu.
Also I have a third one that I haven't touched it yet that chimes but gives no display [no backlight and no signal as the two above]
The fact is that if you boot with a good drive at OS you know that it boots by increasing / decreasing the sound even without any image.
So, anyone had same issue before or has a hint?

[piernov]

Re: 820-2915-B, chimes but no display

I guess you got defective "new" GPUs. It is almost impossible to find a reliable supplier for GPUs…

[dellxps15]

Re: 820-2915-B, chimes but no display

with mobile phone led on lcd do you have image ?

[rookieme]

Re: 820-2915-B, chimes but no display

Well my gpu's are fine as after that I have them installed at a different boards with gpu issue and still work ok.
No I don't have neither image nor backlight, also I have measured the voltages at lvds and they are 0's.
Same issue with external display via display port!

[piernov]

Re: 820-2915-B, chimes but no display

Ok, strange thing indeed… Do you still have GPU VCore?

[rookieme]

Re: 820-2915-B, chimes but no display

Yes I do have PPVCORE_GPU.
My concern is that at 2 cases issue occurred after bga rework [with heat treatment of the board] and issue persists even if I place back the old gpu [that though it had problem before it was able to power on the display].
At the third board I tried a different approach with only trying a good working bios with no luck.
A I'm sure I didn't knok off any parts arroung gpu durring the rework, is there a part that tend to fail after heat treatment? I do use an IR bga station.

[piernov]

Re: 820-2915-B, chimes but no display

Capacitors can fail from heat, especially tantalum here. For example C8942/C8943. Although if they fail, it would mean unstable GPU VCore. I've only replaced a few BGAs so I'm in no way experienced enough to know what could go wrong here.
Maybe the board is heated for too long, or the bottom heater is too cold/hot? The board may start to bend a little bit and it can cause its death.

[rookieme]

Re: 820-2915-B, chimes but no display

Indeed the boards were heated hot enough from bottom heater so that they don't bend during gpu replacement.
I'm also to cautious not to bend the board as ram slot problems occur at theese boards.
So what can happen at 2 boards after heat treatment and at a third one without anyone have it touched before to respond the very same way?


signal like EG_LCD_PWR_EN remains 0

[piernov]

Re: 820-2915-B, chimes but no display

Even though I don't think it's the issue, you should try to replace the tantalum caps around the GPU area (for GPU VCore and CPU VCore, you never know). Also maybe the VRAM is at fault so replace it too (could short signal lines from the GPU and cause it not to work at all). Otherwise I've got no idea.

[rookieme]

Re: 820-2915-B, chimes but no display

I have tried allready with new NRAM's but nothing changed - usually their solders fail and you have dots or lines at display.
Tantalum caps could be a fix but I guess I should measure lower voltages from them in order to be sure that they are failing.

[rookieme]

Re: 820-2915-B, chimes but no display

A clue is that PPVCORE_GPU is 1,1V and should fall down to 0,9V as soon as display shows image but at this case is 1,1V stable

[bushie]

Re: 820-2915-B, chimes but no display

Have you solved the situation?! I have something similar...