Really strange.
If BKLT_SD is high, you should NOT have voltage at all at D7701.
Did you measure correctly?
If BKLT_SD is high, you should NOT have voltage at all at D7701.
Did you measure correctly?
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A1398 820-00138-A no boot
- Thread starter hgoncalves
- Start date
hgoncalves
Active member
Real boardview not available.
820-00163 has some differencies.
In your board, D7701 is placed between coil and filter caps.
D7720 is for keyboard backlight.
820-00163 has some differencies.
In your board, D7701 is placed between coil and filter caps.
D7720 is for keyboard backlight.
hgoncalves
Active member
OK.
On that one ( D7701 ) I have 10V on pin 1 and 45V on pin2.
On that one ( D7701 ) I have 10V on pin 1 and 45V on pin2.
Last edited:
45V is a bit higher than normal backlight voltage.
I think 39V is correct level.
This means you have a problem with video cable, or broken LED strip inside LCD panel.
You may also have bad contacts inside J8300.
I think 39V is correct level.
This means you have a problem with video cable, or broken LED strip inside LCD panel.
You may also have bad contacts inside J8300.
hgoncalves
Active member
Tks.
I have tried with two different known good lcd, and the J8300 is a new one (replaced again yesterday)
I have tried with two different known good lcd, and the J8300 is a new one (replaced again yesterday)
Check which is the correct backlight voltage on working machine.
hgoncalves
Active member
Don't have any other 1398. Is there any other way to be sure?
The Apple logo lights on the top cover?
If not,
"you have a problem with video cable, or broken LED strip inside LCD panel.
You may also have bad contacts inside J8300."
If not,
"you have a problem with video cable, or broken LED strip inside LCD panel.
You may also have bad contacts inside J8300."
hgoncalves
Active member
HI,
I've replaced J8300 again, and now it seams to be always working. AIt should be as you said (bad contact).
TKS!
I've replaced J8300 again, and now it seams to be always working. AIt should be as you said (bad contact).
TKS!
Did you check backlight voltage on the working moment?
Note it, as it will help you in the future diagnostics.
Note it, as it will help you in the future diagnostics.
hgoncalves
Active member
Hi,
Yes I note it and it is 45.7V. I Don't know if this is the right voltage for this model, but in this particularly mac (is the only one that I have here), that is the backlight voltage, on a working state. On future one, I'll compare it.
Thanks.
Yes I note it and it is 45.7V. I Don't know if this is the right voltage for this model, but in this particularly mac (is the only one that I have here), that is the backlight voltage, on a working state. On future one, I'll compare it.
Thanks.
hgoncalves
Active member
Hi,
After all, It doesn't work again. Something very strange is happening:
Once again, after i replaced the J8300 the backlight works for a day or two, but than it stops working.I gues that is someting related with the temperature applied (just guessing).
Any idea of what mite be causing this behaver?
After all, It doesn't work again. Something very strange is happening:
Once again, after i replaced the J8300 the backlight works for a day or two, but than it stops working.I gues that is someting related with the temperature applied (just guessing).
Any idea of what mite be causing this behaver?
What is backlight voltage now.
If higher than normal, there is a problem with the connection with LEDs strip.
If voltage is correct, then you have a problem with the image.
If lower, or missing voltage, then be sure to get image first.
If higher than normal, there is a problem with the connection with LEDs strip.
If voltage is correct, then you have a problem with the image.
If lower, or missing voltage, then be sure to get image first.