Display and backlight not functioning

[alpha76]

Hi,

I have a dear old macbook pro A1398 early 2013 with a smashed display. I bought a replacement screen, attempted to fit it, but i seem to have blown a chip on the motherboard. I did not disconnect the battery cable and the laptop turned on while i was holding the motherboard! Consequently, i cannot get the display to work with either displays. I've watched one of Ross's videos on the same laptop where he repaired the GPU vcore. I have a multimedia to test what i need to. Would i need a schematic of the logic board? Can you help? Many thanks, look forward to your reply.

 

[2informaticos]

Provide us the 820-xxxx code from the motherboard...

 

[JohnB8812]

It?s 820-3332. Does it chime or give a light on a USB mouse? Can you provide a picture of the blown component?

 

[alpha76]

Hi,

The m/b number is 820-3071-A.

It does chime and the USB charges the mouse when i switch the laptop on. No display or backlight though :-(

I cannot see any noticeable blown chips, i was just assuming that i had blown something when i touched the motherboard.

By the way, i have tried several of the resets that i found online and from calling Apple support

 

[2informaticos]

820-3071-A is the code for RIO board. MLB should be 820-3332, Isuppose.

Do you still get steady light on USB mouse if disconnect/reconnect with machine on?
Do you get external video?

Check voltage at pins 9, 28-30 of J9000 (LCD connected).
Be sure L9000 and all FL9000-03 are good.

 

[alpha76]

I have just connected an hdmi to external monitor and i do get a display, albeit not the usual one. It's a grey background with a mouse cursor. THere's no menu or terminal, that i can see..shall i still test the pins?

 

[2informaticos]

You should get the same at internal LCD too.
Disconnect external monitor and measure at J9000 with internal LCD connected.

 

[alpha76]

Do you mean the J9800, i cannot see J9000 on the schematic

 

[alpha76]

Looking at the wrong schematic. I think i have the right one now!

 

[alpha76]

From looking at the schematic the J9000 is the LCD interface connector?

The pins are tiny and im assuming i may need specialised equipement?

All i have is an ordinary multimeter....

 

[2informaticos]

Look at boardview and choose any components for the same pins to test.
Also buy "fine multimeter probes" from any online store...

 

[JohnB8812]

Have you reflowed/resoldered U8900 yet?

 

[alpha76]

I have only just received the probes. Can you confirm what settings are needed for the multimeter?

No, i havent reflowed U8900 !!! Are you suggesting that is what's broken? I was assuming the J9000 was the culprit here??

 

[JohnB8812]

U8900 is a super common cause for this issue on this model. Resolder the joints and reflow it Louis has plenty of videos walking you through how to do it.