MacBook Pro 13.3 mid 2012 - a1278 - no internal display

[EdwardGeo]

Re: MacBook Pro 13.3 mid 2012 - a1278 - no internal display

Platform Controller Hub is

INTEL BD82HM77 SLJ8C

[EdwardGeo]

Re: MacBook Pro 13.3 mid 2012 - a1278 - no internal display

In case if someone will need to know what is inside of lcd pcb. Later will try to dump eeprom. If it will be readable, will share dump.

Also want to check if voltage comes to I2C ic and does voltage comes to resistors which connected to I2C lines on lcd.


I still have idea that pch partially failed or lcd eeprom

[piernov]

Re: MacBook Pro 13.3 mid 2012 - a1278 - no internal display

With LVDS the DDC bus (data&clock) connects directly to the EDID I2C ROM, confirm which one of U102 or U103 it is using continuity mode to LCD connector.
PCH won't send out image anyway if display is not recognized at all.

I already had a dead I2C ROM on an LCD, the 3V regulator went bad along with some other stuff on the board and probably killed it as well.
And I had an LVDS cable with a broken wire for 3V supply of I2C.
And I also had a dead GPU that wasn't communicating properly over the DDC bus for internal panel (but worked fine with VGA).
So anything can happen.

[EdwardGeo]

Re: MacBook Pro 13.3 mid 2012 - a1278 - no internal display

With LVDS the DDC bus (data&clock) connects directly to the EDID I2C ROM, confirm which one of U102 or U103 it is using continuity mode to LCD connector.
PCH won't send out image anyway if display is not recognized at all.

I already had a dead I2C ROM on an LCD, the 3V regulator went bad along with some other stuff on the board and probably killed it as well.
And I had an LVDS cable with a broken wire for 3V supply of I2C.
And I also had a dead GPU that wasn't communicating properly over the DDC bus for internal panel (but worked fine with VGA).
So anything can happen.

U102 is EDID eeprom, flash reading perfect. Made dump, attached, possibly someone will need it.

So for some reason chipset is not reading EEPROM. I2C read address is the same as i get at capture with Sealogic, but eeprom not sending data back.

So possibly the PCH is doing wrong calls? Or data corruption. Or possibly some IC is failed and that stopping EPPROM send data to master?


I think that is time to order PCH replacement. I will try to debug this line on other macbook not pro.

The only explanation is a short inside of cable that partially harm DDC data line, thats why PCH cant send proper read request and eepprom isn`t recognize it.


U102-EDID-B133EW07 V2
IMAGE of I2C connection
B133EW07-V2-AUO

[EdwardGeo]

Re: MacBook Pro 13.3 mid 2012 - a1278 - no internal display

But if pch asking eeprom to access data then pch ddc signals present, and if eeprom can be also read at address 0x50h by programmer then something prevents load of edid but logic are working. Really weird situation


Is it possible that some ic is protecting pch from failure or other method used!?

The only short I have found inside of cable is led return wire...

[EdwardGeo]

Re: MacBook Pro 13.3 mid 2012 - a1278 - no internal display

Good news. I think i had found the true nature of issue. Look at image.


After read protocol of PCH begin, the PP3V3_S0_LCD_F goes to zero volts and the request by pch is not working as EDID eeprom is restarted.






So problem should be in L9008 or C9010
L9008 resistance = 5.97 kOhm - 0402-LF 120-OHM
L9004 resistance = 0.09 hOhm - 0402-LF FERR-120-OHM

[EdwardGeo]

Re: MacBook Pro 13.3 mid 2012 - a1278 - no internal display

Tada




Edid from another display successfully load.
Will order that fuses and will continue repairing!

Thanks for time and support!

[EdwardGeo]

Re: MacBook Pro 13.3 mid 2012 - a1278 - no internal display

After edid arrived, all lvds voltages rises.

So decided to check if lcd will work and it does