Re: Macbook Pro A1990 (820-01814) no backlight display
Hello world! Sorry for my absence, I was practicing with my new soldering station. While I'm waiting for the new [B]LP8548[/B] chips, I want to show you what I found on my board. To your attention [B]C8461[/B], on which I found cracks, although there is no short circuit when checking with a tester, I do not know. And also [B]C8441[/B], which seems to be raised and I'm not sure about this element (when measured at 1 pin, the tester shows 5V, if my memory serves me). I am also attaching a photo of the [B]LP8548(U8400)[/B] landing...
XVLZ
Member
Last Activity: 07-27-2023, 12:54 PM
Joined: 11-18-2022
Location: London
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Re: Macbook Pro A1990 (820-01814) no backlight display
Hello world! I'm back, I finally got my soldering station and now I can learn the basics. Unfortunately, I have not been able to purchase a microscope yet, so I can only warm up the U8400 from the current tasks, as well as replace the L8410, I will do this one of these days and share the results.Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
Hello World! I think I need my own soldering dryer, now I don't have time to deal with my macbook, my friend who owned all the necessary equipment quit the service and now I have no one to turn to for help with soldering. Now I am developing a website for my client, I work from an old laptop on Windows, the sooner I hand over the work, the sooner I can buy myself soldering equipment, including a microscope. Please don't close the thread, I'll be back later with news. Happy new year everyone btw 🎉Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
now I can't solder the U8400 backlight chip and the L8410 inductor, because my friend with the equipment went on vacation, I hope I will solve this problem soon, as soon as I start soldering, I will report the results after.Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
I measured relative to the ground without power and display, the motherboard was removed from the case, the black probe to the ground, red to pin 1, then the same thing but to the second pin...Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
I measured the resistance of the L8410 relative to ground, and got ~0.7 ohm, given that the circuit should already be ~0.47, I get about 0.23, which is close to the value of the inductor
so this item is probably correct.Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
and yet, if the problem is really in the U8400, can the webcam not work?Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
I confirm, U8400 was replace
thanks for the help, tomorrow we will try to test the U8400 soldering, I will report the results later
upd
Can the L8410 affect the backlight? even before the replacement of the U8400, it attracted my attention, tell me how can I check the L8410?
upd 2
is there any difference in LP8548B1SQ-03?
before replacement, I had an IC marked 48B1-03, I ordered an IC for my model, but the new one was marked 48B1-04, does it matt...Last edited by XVLZ; 12-25-2022, 06:31 PM.Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
what else can i measure to make sure the problem is really in the U8400?Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
you are right... actually R8442 has 0 resistance...
I measured relative to the ground, by analogy with your previous attachments (when we measured R9833)
ps dead end again, I already hoped that we found a solution
Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
I was going to solder it tomorrow, I haven't touched it yet, I just did a back test of R8442 and got 3.3 V on both sides, I'm confused
upd
but resistance mode R8442 still 47 kohm at both pins, this is normal?
upd 2
I thought if R8442 has a resistance of 47 kOhm, then it should not show 3.3 VLast edited by XVLZ; 12-25-2022, 04:35 PM.Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
i'm confused, just now i decided to check pin 2 of R8442 again and got 3v...Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
then what is the role of this resistor? is it okay if we directly connect two pins? Could this affect the performance of the laptop in any way? Or is it better to replace it with a new one?Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
2 pin R8442 also 47 kohmLeave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
yes I checked again, really 47 kohms (all power off)
resistance mode 200k
So the backlight malfunction can only be in this resistor?
do you have the part number for this resistor? so i can buy it and replace it(R8442)
upd
or I just need to remove it and connect directly pin 1 and pin 2 of R8442?Last edited by XVLZ; 12-25-2022, 03:49 PM.Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
done
R8442, pin #1 = 3.3 V
and 47~ 200k ohm resistence modeLeave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
@ R9833, pin # 2 = 3.33 VLeave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
done...Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
0
upd
the display cover is open, the motherboard is powered by type c charging and connected to the display...Last edited by XVLZ; 12-25-2022, 02:51 PM.Leave a comment:
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Re: Macbook Pro A1990 (820-01814) no backlight display
done...Leave a comment:
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