820-00163 no backlight

[Outofwhack]

Hi,

I bought a 'working board' on ebay but seller left heatsink on and a jolt in transit has caused the video connector to be demolished and 8 resistors/capacitors to be wiped off.

These are now replaced, I get POST, fan spins and I can see login on the lcd with the aid of a torch but there is no backlight.

It seems Q7706 is not being told to turn on.
I don't have a spare screen to try.
Don't know what to try next - help

signal	When powered	Diode mode
ppvout_s0_lcdbklt	0v
bklt_en	3.3v
pp5v_s0_bklt_vddd	5v
F7700	not blown
Q7706 pin4	12.58v
Q7706 pin 1,2,5,6	0v		Not in on state
Q7706 pin 3 (lcdbklt_en_l)	12.48v		When does U7701 ground BKLT_SD?
R7702	63k
R7701	81k
bklt_scl	5v	0.45v
bklt_sda	5v	0.45v
R7708	18k
R7709	150k

 

[2informaticos]

Apart of enable, U7701 requires proper communication with LCD assembly.
T-CON is in the middle between PCH and U7701; for backlight adjust, I mean.

Check R7747/58 and their traces.
If OK, need to test with known good LCD assembly.

 

[Outofwhack]

Sorry, what does T-CON mean?

Another factor I should have mentioned I am using an 820-00163 to replace a 820-00426. Although I paid for the latter they sent the former.
In other words the LCD screen was from an A1398 running with an 820-00426.

Ive verified the pinout on the video connector - they are identical.
Should this work or would there be a mismatch between board and LCD assembly?

This is the first ever video connector Ive soldered on a board and Im not very good.
First thing the I-PEX I bought doesn't have tags to sit flush with the board at the ends so I had to use a lot of solder.
I am not real happy with the way the male seats in but I am seeing video.

	value	trace good
R7747	0 ohm	yes
R7758	0 ohm	yes

As mentioned I have no other LCD to try.
Is it safe to ground BKLT_SD at U7701 to see if backlight on LCD turns on?

 

[2informaticos]

U7701 will pull-doen BKLT_SD when is "happy" with I2C communication.
T-CON is electronic part inside LCD assembly.

15" retina screens should match the board; which is not your case.
Get compatible screen for test.

 

[Outofwhack]

I assumed the same screen would suit any of the logic boards that might occupy a mid 2015 15inch MacBook Pro e.g. whatever their graphics provision.
Is this wrong?

If you mean I have a mismatched screen and board - is there a document that would tell me what model MacBook a 820-00163 board works with? Perhaps it can give life to a broken MacBook bought cheap.

 

[2informaticos]

15" 2015 LCD is unique and not compatible with previous models.