HTR-Informatique
New member
The screen works, it does not worry when I test with other motherboards.
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MacBook Air 13" A1466 820-00165 - Backlight
- Thread starter HTR-Informatique
- Start date
Do you get BKLT_EN and BKLT_PWM at U7701?
Did you try PRAM reset several times?
Did you try PRAM reset several times?
HTR-Informatique
New member
On BKL_EN I have 2.5 / 2.6V.
On BKL_PWM I have 2.8V.
Yes, I reset the PRAM several times.
On BKL_PWM I have 2.8V.
Yes, I reset the PRAM several times.
HTR-Informatique
New member
On R7731, I have 8.5V on pin 1 and 2.5V on pin 2.
On R7715, I have 2.5V on pin 1, but nothing on pin 2.
On R7715, I have 2.5V on pin 1, but nothing on pin 2.
"On R7715, I have 2.5V on pin 1, but nothing on pin 2."
Don't you want to get voltage on ground pin, no?
BKL_EN should be 1/3 of PPVIN_S0SW_LCDBKLT, which is (should be) aprox 8.5V.
You should get 2.8V aprox; but even 2.5V is sufficient to enable U7701.
I suppose bad solders for U7701, or bad chip.
Post resistance to ground (diode mode, red probe to ground) for all the connections of U7701.
Use surrounding components as test points...
Don't you want to get voltage on ground pin, no?
BKL_EN should be 1/3 of PPVIN_S0SW_LCDBKLT, which is (should be) aprox 8.5V.
You should get 2.8V aprox; but even 2.5V is sufficient to enable U7701.
I suppose bad solders for U7701, or bad chip.
Post resistance to ground (diode mode, red probe to ground) for all the connections of U7701.
Use surrounding components as test points...
HTR-Informatique
New member
Hello, yes the pin 2 is GND.
I tested the pins of U7701, no worries, I tested the continuity, see if there were no tracks cut, I did not test the continuity to the ground for all the pins.
I sold a new brand new chip bought on Farnell.
Still no backlight.
I still have 8.5V on XW7720.
I tested the pins of U7701, no worries, I tested the continuity, see if there were no tracks cut, I did not test the continuity to the ground for all the pins.
I sold a new brand new chip bought on Farnell.
Still no backlight.
I still have 8.5V on XW7720.
"Post resistance to ground (diode mode, red probe to ground) for all the connections of U7701.
Use surrounding components as test points..."
Do that, so we can confirm good solders...
Use surrounding components as test points..."
Do that, so we can confirm good solders...
HTR-Informatique
New member
I have tested all U7701 pins to earth, except the GND pins, no other is grounded, no resistance to the multimeter (infinite resistance).
I also took the opportunity to note all the tensions of U7701 with a monitor plug:
1: GND
2: GND
3: 2.5V
4: 2.81V
5: 8.54V
6: 8.55V
7: 8.55V
8: 0V
9: 0V
10: GND
11: 5,10V
12: 0V
13: Impossible to test (I do not see where is the pad to test it)
14: 3.30V
15: 0V
16: 5,10V
17: 0V
18: 3.30V
19: 3.30V
20: 0V
21: 0V
22: 0V
23: 0V
24: GND
25: 0V
I also took the opportunity to note all the tensions of U7701 with a monitor plug:
1: GND
2: GND
3: 2.5V
4: 2.81V
5: 8.54V
6: 8.55V
7: 8.55V
8: 0V
9: 0V
10: GND
11: 5,10V
12: 0V
13: Impossible to test (I do not see where is the pad to test it)
14: 3.30V
15: 0V
16: 5,10V
17: 0V
18: 3.30V
19: 3.30V
20: 0V
21: 0V
22: 0V
23: 0V
24: GND
25: 0V
You didn't understand.
Diode mode value on the U7701 pins (red probe to ground) will reveal if you have some bad solder.
Please do what we ask, if you expect help.
WE can NOT measure anything on YOUR board...
Diode mode value on the U7701 pins (red probe to ground) will reveal if you have some bad solder.
Please do what we ask, if you expect help.
WE can NOT measure anything on YOUR board...
HTR-Informatique
New member
If I understand correctly, I have to put the multimeter in diode mode, the red (+) on the mass, and with the black (-) I test each point of U7701?
I should have what value if good / bad solder on the multimeter?
I should have what value if good / bad solder on the multimeter?
Better we try to interpret your values.
Do not exist precise readings.
The values vary, depending on each board and multimeter used...
Do not exist precise readings.
The values vary, depending on each board and multimeter used...
HTR-Informatique
New member
Hello,
Sorry for the wait, I was working.
I attach the photo of my multimeter with the diode setting used.
So:
1: .016
2: .016
3: .712
4: .679
5: .824
6: .512
7: .512
8: 1.
9: 1.
10: .687
11: .562
12: 1.
13: I can not test it, no pad
14: .460
15: 1.
16: .562
17: 1.
18: .712
19: .715
20: 1.
21: 1.
22: 1.
23: 1.
24: .016
25: 1.
Sorry for the wait, I was working.
I attach the photo of my multimeter with the diode setting used.
So:
1: .016
2: .016
3: .712
4: .679
5: .824
6: .512
7: .512
8: 1.
9: 1.
10: .687
11: .562
12: 1.
13: I can not test it, no pad
14: .460
15: 1.
16: .562
17: 1.
18: .712
19: .715
20: 1.
21: 1.
22: 1.
23: 1.
24: .016
25: 1.
Attachments
You'r multimeter definitely has a problem; 016 from ground to ground???
"15: 1.
-------
20: 1.
21: 1.
22: 1.
23: 1.
--------
25: 1."
All these balls unsoldered; probably many more.
Reflow the chip...
"15: 1.
-------
20: 1.
21: 1.
22: 1.
23: 1.
--------
25: 1."
All these balls unsoldered; probably many more.
Reflow the chip...
HTR-Informatique
New member
I flatly change the chip in the end, the same.
Maybe it is actually poorly welded but I even reflect the chip several times and always the same.
Possible that the problem comes on the other hand?
Maybe it is actually poorly welded but I even reflect the chip several times and always the same.
Possible that the problem comes on the other hand?
Return lines should gave all same value, 600-650 aprox (diode mode); if chip is properly soldered.
I hope you remember to always ckeck with red probe at ground...
I hope you remember to always ckeck with red probe at ground...
HTR-Informatique
New member
The chip is well soldered, no worries.
Still no backlighting though.
When I run the tests while pressing D at startup I have the error PFM006: the SMC present can be a problem.
I did a reset SMC and PRAM / NVRAM but nothing.
Still no backlighting though.
When I run the tests while pressing D at startup I have the error PFM006: the SMC present can be a problem.
I did a reset SMC and PRAM / NVRAM but nothing.
Post again the diode mode values for U7701.
I hope you didn't forget to check XW7720; many mentions on the forum about it (pictures too)...
I hope you didn't forget to check XW7720; many mentions on the forum about it (pictures too)...
HTR-Informatique
New member
Now post U7701 voltage; C1, C4, A3, A4.
LCD connected, of course...
LCD connected, of course...