820-3115 not recognizing screen

[Chuck60]

Hi I was working on a water damaged board and I relplaced a few items on 5v/3v rail. It chimes now and I have CPU activity mouse flashing. but no display I’m missing J9000 ( pin 3 0v, pin 4 3.3v) LCD_PWR_EN 0v at U9000 and SMC_LID is 3.4v L9080, r9008, r9009, L9004 all measure good so I’m guessing the lcd isn’t being “seen” I’m using a b133ew07 test screen and a “new” screen cable. if I remember the screen is from a 2010 MacBook Pro so I’m guessing this set up should work if I’m wrong let me know.

 

[2informaticos]

Test voltage at LVDS_DDC_CLK/DATA lines.
Check if both R9008/9 are good.
Be sure to test with compatible screen.

 

[Chuck60]

I’m sorry it was incompatible screen thank you for your time

 

[Chuck60]

Ok I received the right screen today
I have backlight now but no image LVDS_DDC_CLK/DATA= 0v all
R9008, r9009 are with in spec I tested traces to and from the Filter/choke to lvds and from the test points They are all good. I have 95ohms between 17/18 on lvds With screen plugged.

 

[2informaticos]

"LVDS_DDC_CLK/DATA= 0v all
----------------------------
95ohms between 17/18 on lvds With screen plugged."
Check voltage and diode mode without LCD connected.

 

[Chuck60]

J9000 pins
1- gnd
2-.582
3-.582
4-.339
5-OL
6-.610
7-.560
8-.600
9-.627
10-gnd
11-gnd
12-.628
13-.gnd
14-gnd
15-.605
16-.gnd
17-gnd
18-.606
19-.gnd
20-gnd
21-.577
22-.577
23-.577
24-.615
25-.615
26-.585
27-.585
28-.585
29-.585
30-OL

LCD unplugged voltages

Pins 2& 3 0v
Pins 6&7 0v
Pins 17&18 0v
Pins 20&21 3.5v

Lcd plugged in :

Pins 2& 3 3.3v
Pins 6&7 3.3v
Pins 17&18 0v
Pins 20&21 27.99v

 

[2informaticos]

"I have backlight now but no image LVDS_DDC_CLK/DATA= 0v all"
And what this mean???
Looks like you have backlight.

 

[Chuck60]

I’m not sure of what you’re saying.
I have backlight the screen is dim.
Apple logo on back of screen is glowing but no image or Apple/ flashing folder.
You asked me to check LVDS_DDC_CLK/DATA I checked and it had 0v. I thought I was having no image

J9000 pins 24-29

LED_RETURN_1 =.681v
LED_RETURN_2 =.682v
LED_RETURN_3 =.681v
LED_RETURN_4 .=681v
LED_RETURN_5 =.683v
LED_RETURN_6 =.824v

 

[2informaticos]

"I have backlight now but no image LVDS_DDC_CLK/DATA= 0v all
---------------------------------
Pins 6&7 3.3v"
Is not strange enough for you???

Forget LED return, or other backlight stuff; you've got backlight.
Check L9080.

"95ohms between 17/18 on lvds With screen plugged"
Still the same?
If yes, change LCD assembly...

 

[Chuck60]

Ok I replaced it L9080 will try another lcd assembly could it also be the lvds?

 

[2informaticos]

If you get 95 ohms between pins 17/18 ONLY with LCD connected, guess what.
Could also be an internal issue inside J9000; present only when video cable is inserted.

 

[Chuck60]

Ok I’ll first try with just the Lvds cable with no screen connected. I will try the screen on another dead board for measurement sake if I get 95ohms then I know for sure it’s the assembly. I’m thinking more like it’s the lvds connector :/

 

[Chuck60]

ok I fixed the dead board and this screen does indeed work. So what can it be ? Bad PCH ? LVDS connector?
Maybe I should Have startEd with what I worked on. Maybe I messed something up I repaired u6100, u7760, u7780, Q3380, f9700. I got these for $5 each so they where missing parts and or badly damaged If you would like pictures of these areas I can send some
Thank you for your help you have taught me a lot and I appreciate your help. I understand how frustrating it must be talking with a novice

 

[2informaticos]

Post voltage and diode mode on pins 2/3, 4, 6, 7, 17, 18, 21/22, with LCD connected.
Do you still get 95 ohms there?

 

[Chuck60]

——--Diode. Voltage
Pin 2 .462. 3.3v
Pin 3 .462. 3.3v
Pin 4 .333. 3.28v
Pin 6 .525. 3.28v
Pin 7 .561. 3.28v
Pin 17 .363. 0v
Pin 18 .351 0v
Pin 21 .570. 26.98v
Pin 22 .570. 26.98v
Pin 22 .570. 26.98v
still 95ohms

 

[2informaticos]

Do you really need to check pins 2/3 and 21/22 by separate???
Please try to understand a schematic and do not waste time with redundant measurments.

27V at pins 21/22 is good voltage for backlight.
3.3V at pins 2/3 is also good for LCD matrix.
All is possible only if LCD is correctly recognized.

Your problem must be the 95 ohms between pins 6/7.
If this appears only when video cable is connected, then you have a problem with LCD connector, video cable, or LCD display.
As you've said LCD assembly works with other board, then the only option is bad LCD connector.

BTW, check resistance between pins 6/7 in the other board and compare values...

 

[Chuck60]

Ok I’ll checked it again. but my working board also had 95ohms. When I connect the screen :/ I powered it up the screen works and powered it down removed from power and test 17/18 it’s still 95ohms.
I understand 2/3, 21/21 pins are connected but I just check it and post The values separately. Redundancy is my life’s work

 

[2informaticos]

Allow 10-15s (at least) after power is removed, before measuring diode, or ohm mode.

 

[Chuck60]

Ok thanks will do

 

[Chuck60]

Ok I Have PPVCORE_S0_AXG=0V it never comes up.

I waited like a hour took the reading in front of filter on 17/18 on test point before it goes to the other side of the board all test between 95- 98 ohms higher values the further from the connector. This ddc/data line has been bothering me since I got this I’ve expected some sort of voltage on this line. Is it either waiting for some sort of handshake or data? Then Pch sends Out signal ? Anyway I ordered a new connector already.