(347) 552-2258 [email protected]

820-2936 - Works but

menatwork

menatwork

New member
Guys, I think this is super easy, but i cant figure out alone (beginner).
I Get chime and everything with external monitor.
Just screen, i get everything but, but i have back light..

j9000:

pin 22 - 12.56v
pin 2,3,4 = 3.27v
pin 5 = 0v

Do you guys have something like that? Let me know.
 
Last edited:
D

dukefawks

Administrator
You cannot have backlight with 12V on the output!

Do a PRAM reset, then:
First check SMC_LID, then check BKL_EN and BKL_PWM they should all be high. Check corrosion under/around the LP8550
 
D

dukefawks

Administrator
BKL_EN should be at least 2.6V. It is a simple resistor divider, so either R9731 is dead or the LP8550 is pulling it down. First check resistance to GND on BKL_EN, if it is less than lets say 60K the LP8550 is dead.
 
menatwork

menatwork

New member
Q9706

Pin 1 : Start 3 and drop to 0 - PPBUS_SW_LCDBKLT_PWR
Pin 2 : Start 3 and drop To 0 - PPBUS_SW_LCDBKLT_PWR
Pin 3 : 12.22v - PPBUS_EN_DIV
Pin 4 : 12.60v - PPBUS_SO_LCDBKLT_FUSED
Pin 5 : 2.60 and drop - PPBUS_SW_LCDBKLT_PWR
Pin 6 : 0.64 - PPBUS_SW_LCDBKLT_PWR
 
larossmann

larossmann

Administrator
Staff member
Q9706 is a P channel MOSFET meaning it won't open unless the voltage on pin 3 is less than pin 4.

R9788/R9789 is a voltage divider designed to send 5v to pin 3 of Q9706, so that it can turn on. However, it can only function as a voltage divider if the bottom resistor, R9789 has a path to ground, or else it will just send pin 4's 12.6v to pin 3 of Q9706.

Q9707 determines whether R9789 gets to have a path to ground. This is a dual N channel MOSFET - it will allow power from source to drain when the voltage on the gate is higher or the same as the voltage on the source. Here the source is ground, which is 0, so anything on the gate will likely open it.

So one of four things is occuring here.

1) C9782 is shorted and fucked, causing 12v to always be on pin 3 of Q9706.

2) R9789 is corroded/burned/bad.

3) LCD_BKLT_EN or BKLT_PLT_RST_L are missing <--- this is usually the case when the machine does not see the screen

4) Q9707 is fucked/bad.

5) Q9706 is fucked/bad shorting pins 3 and 4 together.

Seeing as you claimed you had no image, we should be troubleshooting no image rather than no backlight I feel. However, since you said you had backlight with 12v on backlight, which is impossible, I have no idea what it is you are seeing at this point, as the light will not turn on without 26-27v on this model...
 
D

dukefawks

Administrator
You told in the first post you had 12.6V at pin 22 of LCD connector. Now you post values that Q9706 is not even turning on. This all makes no sense.....
 
menatwork

menatwork

New member
After i replaced U9701 - R9715 and i get that V in Q9706 and pin 22.
I just try do your advice.

U9701 is new.
 
menatwork

menatwork

New member
C9782 - PPBUS_SO_LCDBKLT_FUSED PIN 1 - 12.59V
C9782 - LCDBKLT_EN_DIV - PIN 2 - 11.60V
R9789 - 147K OK

Q9707:
- Pin 2:BKLT_PLT_RST_L: 3.30V
- Pin 3:LCDBKLT_EN_L : 9.85V
- Pin 4 LCDBKLT_DISABLE: 0v
- Pin 5 LCDBKLT_EN: 0v
- Pin 6:LCDBKLT_DISABLE 0v
 
menatwork

menatwork

New member
​dukefawks larossmann I get that:

C9782 - PPBUS_SO_LCDBKLT_FUSED PIN 1 - 12.59V
C9782 - LCDBKLT_EN_DIV - PIN 2 - 11.60V
R9789 - 147K OK
Q9707:
- Pin 2:BKLT_PLT_RST_L: 3.30V
- Pin 3:LCDBKLT_EN_L : 9.85V
- Pin 4 LCDBKLT_DISABLE: 0v
- Pin 5 LCDBKLT_EN: 0v
- Pin 6:LCDBKLT_DISABLE 0v
 
D

dukefawks

Administrator
LCDBKLT_EN should of course be high and has nothing to do with U9701. I bet the whole LCD is not recognized at this moment and there is no image at all.
 
D

dukefawks

Administrator
WAIT WTF!!! I just watched the video and the backlight turns on! How else do you think the Apple logo lights up??? This means all your measurements are BULLSHIT.
The backlight works, the LCD is just not making an image. This is an LVDS issue. Measure all LVDS lines on diode mode. I bet L9080 is missing/damaged or the connector is fucked.
 
Last edited:
menatwork

menatwork

New member
Just Backlight, no video like i said before.
Thats why i try figure out with you. I'm not engineer, but i know how to measure things.
I try 3 different LCD and nothing happen.
 
You must log in or register to reply here.
Top