MBP A1502 no image on screen

[mushr00m]

MBP A1502

No image on screen, BUT with external monitor its working 100% fine

SINCE I do not have same MBP A1502 screen to test and check if its BAD screen. Is there any other test that I could make?

Can I test an old A1278 screen on this model to check?

Any other method to test before going to buy a new screen without 100% being SURE?

 

[2informaticos]

A1278 models use LVDS screens, and A1502 eDP instead.
More than that, 2015 model is unique; not compatible with previous A1502 variants.
Not sure what board do you have there; is a must post in the title.

 

[mushr00m]

Hi

Its a 820-4924-A

Tested with a new screen and same behavior!

BTW the camera work fine!!

Looks like its something bad on the board!

 

[2informaticos]

"Tested with a new screen"
2015 LCD assembly for sure?
It is not compatible with previous A1502 from 2013/14.

 

[mushr00m]

Yes

I bought a brand new A1502 2015 assembly display!

 

[mushr00m]

I can record a video if you want!

 

[2informaticos]

New doesn't mean known good.
With original screen missing image and backlight at same time?

Do you get 3V at pin 5/J8300?
Also check for 5V at pins 28-30, at least in the first seconds (when chimes).
LCD_HPD_CONN should go high at same time; if LCD is connected and correctly recognized.

 

[mushr00m]

Just noticed with the new screen that is a backlight problem.

Where should I look for?

Weird that with the original screen I didnt get a backlight problem

 

[2informaticos]

As I said, you must be sure this screen is for 2015.
Or you never get backlight.
Find another KNOWN GOOD 2015 screen for test.

 

[mushr00m]

I bought described as 2015 BRAND NEW... I am not sure if its KNOWN GOOD cause I do not have another computer to test to

However the original one doesnt have backlight and image
this BRAND NEW doesnt have backlight

What options do I have?

Buy another one? LOL I am out of money I bought this one after coming here asking for solution

To really test with a KIND OF KNOW GOOD since its a new one

 

[2informaticos]

Known good no need to be perfect.
Keep damaged screens for test in service.
Broken screen, but which you know got backlight before replaced is perfect for test.
The problem is to mark the compatible year on the broken test screens; once you remove from the machine.

Do you actually get any voltage at pin 1/J8300?
BKLT_EN_R is present?

 

[mushr00m]

I do not have any broken screen for this model to keep and test. I usually keep broken stuff if is TESTABLE.

PIN 1 J8300 = 0V
BKLT-EN_R = I measured on a TP on the side of the board, since the components are on the back of the board and not possible to measure without dissamble it. I hope this TP is related to the backlight

If you see the picture of the board its the only one that appears below L7720 and it gives me 4.50V

 

[mushr00m]

 

[2informaticos]

Please, a bit of imagination.
Who impede you to connect the screen to the board out of shell?
You don't need to connect anything else; no TP, nor SSD.

 

[mushr00m]

Why would I do everything without the shell if I can do it in the fastest way?

 

[mushr00m]

if the TP is the right one.

DONE

I am not sure since on the board view it appears a lot, but you are the MASTER here!

If this TP is not the right one, OK I will dissamble the board!

 

[2informaticos]

You may need to check more points on the backlight circuit.
Some of them will be available ONLY on the other side.

The boardview shows many more test points in that area; not seen on your picture.
Are you sure that is BKLT_EN_R and not BKLT_SDA???

"Fastest way" will be to test with known good compatible screen.
You may waste time with a good working board in fact.
Try to find 13" 2015 broken screen (with good backlight) in other service center, or second hand auction websites.
Is good to have it in stock for future repairs.

 

[mushr00m]

The boardview shows many more test points in that area; not seen on your picture.
Are you sure that is BKLT_EN_R and not BKLT_SDA???

I AM NOT SURE... That's why I ask the MASTER!

I do not have a way to buy GOOD KNOWN WORKING SCREEN

I spend A LOT of money on a new one, brand new, which I guess its 100% working
A1502 2015 BRAND NEW SCREEN

I will dissamble the board and give you the measurements that you requested... Any other measurement that you are looking?

 

[2informaticos]

"I AM NOT SURE... That's why I ask the MASTER!"
Do you expect that I will get 4924 board and confirm in continuity mode what test point is?
Why don't do it yourself?

"Any other measurement that you are looking?"
Post BKLT_EN_R first.

"I do not have a way to buy GOOD KNOWN WORKING SCREEN"
I mentioned broken screen, but with working backlight.

BTW, where did you buy the new 2015 screen?

 

[mushr00m]

Just found out that below U7700 had corrosion and PIN 1 was damaged

Make a jumper and put back the same IC still the same behavior

Can I use a LP8561B0SQ from an iMac board 820-4668?

I think its the closest one I have here and I do have some A1278/A1466 donor boards.