Macbook pro A1278 no picture on the screen

[String2016]

This is the first time to repair mac book, I need help on this to guide me to repair this please. This is MAC BOOK PRO A1278 EMC2554, the problem is pressing power button i heard the chime sounds and there is light on the screen but no picture, i tested both screen and flex to another mac screen is ok.can anyone help me guide to repair this please thanks in advance

[ktmmotocross]

Re: Macbook pro A1278 no picture on the screen

test lcd power. i think u r missing 3.3v power for it. check schematic

[String2016]

Re: Macbook pro A1278 no picture on the screen

thanks for the response, could you guide me where to check please

[ktmmotocross]

Re: Macbook pro A1278 no picture on the screen

on lvds connector

[String2016]

Re: Macbook pro A1278 no picture on the screen

thanks i check on lvds connector PP3V3_LCDVDD on pin2 and pin 3 no voltage. where to check next please

[ktmmotocross]

Re: Macbook pro A1278 no picture on the screen

look at the schematic where it comes from, i supose there is switching mosfet

[String2016]

Re: Macbook pro A1278 no picture on the screen

does the mosfet connected is the U9000?

[ktmmotocross]

Re: Macbook pro A1278 no picture on the screen

dont know there are lot of A1278 boards.

[String2016]

Re: Macbook pro A1278 no picture on the screen

anyone can help me on this please

[ktmmotocross]

Re: Macbook pro A1278 no picture on the screen

post right schematic or board marking

[SMDFlea]

Re: Macbook pro A1278 no picture on the screen

Have you tried a PRAM and SMC reset .

[String2016]

Re: Macbook pro A1278 no picture on the screen

the board has marking 820-3115-B

[String2016]

Re: Macbook pro A1278 no picture on the screen

@SMDFLEA i did not tried PRAM AND SMC RESET. this mac working on external display

[ktmmotocross]

Re: Macbook pro A1278 no picture on the screen

u9000 is actually that switch. check its input and output, ON signal

[String2016]

Re: Macbook pro A1278 no picture on the screen

thanks ktmmotocross the problem is i cannot find the U9000 on the board located

[ktmmotocross]

Re: Macbook pro A1278 no picture on the screen

https://www.badcaps.net/forum/attach...3&d=1468078887

[String2016]

Re: Macbook pro A1278 no picture on the screen

file has a password and how to open this file

[ktmmotocross]

Re: Macbook pro A1278 no picture on the screen

https://www.badcaps.net/forum/attach...1&d=1481251744

[piernov]

Re: Macbook pro A1278 no picture on the screen

Screen needs to be recognized in order to get power on pin 2/3. It gets recognized from the DDC bus, on pins 6 and 7. DDC is powered on pin 4.
Basically, you need 3.3V on pin 4 before anything.
You need the LCD to be plugged in to measure voltage on the connector.

Check for liquid around LCD connector and make sure it's not damaged.

[String2016]

Re: Macbook pro A1278 no picture on the screen

i measured the voltage with lcd plugged in