820-3662-A No Screen but backlight

[blob810]

Hello community,

i read a lot of interesting threads the last days here and i decided to register myself and i hope someone can help me with a Macbook Pro 15" mid 2014.

From one day to the other the macbook wont start. I unplugged the battery, ssd and pressed the power button for 15 seconds. Then I connected everything again and the macbook started, but the internal display stays black. I checked the mainboard and saw that the capacitor C7333 was broken. I replaced it with a new one, but still no picture on the screen, but backlight. I can start the device with an external monitor but only when the lid is closed or when i unplug the internal lcd from the board. I tested also another lcd - same problem.

On L8300 Pin 2 has 5V when chiming.
J8300 Pin 9 has 2,8V.

Any tips.

Thank you.

 

[2informaticos]

So now is black screen, or "pure" white?
Check continuity for all FL8300-3 coils.

 

[blob810]

first, thanks for your fast reply.

screen is completly black, apple logo is shining so backlight is on.
capslock and usb activity working.

i measure when i´m at home

 

[JohnB8812]

Tried a known good screen? This sounds like a bad screen to me...

 

[blob810]

I tested also another lcd - same problem.

No success.

 

[JohnB8812]

Oh I see I missed that. Definitely no question mark folder without the SSD plugged in? If so, I would say try another BIOS for testing first.

 

[blob810]

I searched for the FL830x coils. And I think I found the problem. FL8303 is not there. Its cracked in the middle on both lines. Does anyone can give the part number of it to order or a comparable coil.

 

[2informaticos]

Just run some tiny wires instead...

 

[blob810]

That was the main failure. I placed some tiny wires on it and it worked for when i tested it. Then i want to resolder the wires because i was not happy with it. Now i have no backlight. I measured on the C7715-C7717 and i have 0V on it.

Edit: On F7700 i have my 12V

Edit: On Q7706
Pin 1 - 0V
Pin 2 - 0V
Pin 3 - 12V
Pin 4 - 12V
Pin 5 - 0V
Pin 6 - 0V

 

[2informaticos]

Did you connect LCD when measure that?
Check what you did wrong when solder...

 

[blob810]

I already disconnected the wires which i soldered on the board to restore the state when backlight was working.
I measured with connected LCD.

 

[2informaticos]

If you didn't touch anything else, check again FL8303 pads.
Be sure no low resistance to ground.
Post voltage for J8300, pins 28-30, 9.

 

[blob810]

FL8303 pads are lost, so the last parts in this data lines are C8327 and C8326. I try to figure out why the backlight is not present anymore. After that i´ll solder the the wires back to bridge the FL8303.
On J8300 i pin 28-30 i have 4.4V and on Pin 9 only 1.8V.

 

[2informaticos]

"On J8300 i pin 28-30 i have 4.4V"
Which voltage do you get without LCD connected?

 

[blob810]

5V without display, but it´s working now again.
I put the wires back between C8326 <-> R8318 and C8326 <-> R8317 and now it´s working with only lcd and board.
I put tonight everything together in the housing and will report. Thank you.

 

[blob810]

Is there a reason why i have only 4.4V on Pins 28-30 when lcd is connected and working? At the same time i have 5V on L8300 on both pins.

 

[2informaticos]

Bad contact of DMM probes to pins, or bad solders on J8300...

 

[blob810]

Bad contact of DMM probes to pins, or bad solders on J8300...

But with the same probes and on the same pin, i have 5V when no lcd is connected when the macbook is chiming.

 

[2informaticos]

Then check the trace from L8300 to J8300.

BTW, do NOT quote an entire post from few cm above...