820-00244 no trackpad and keyboard

ajdoc

Member
Details from client:
Device had liquid damage on keyboard.
He opened the MacBook but then he disconnected trackpad flex from logic board there was small smoke near connector on board.
Before that trackpad was working fine - just some of the keys was not working.
Now any key on keyboard (except power button) is not working, keyboard is not detected by system. Trackpad is only clicking, no moves.

Got new keyboard but same story.
With disconnected keyboard trackpad still wont move, but it clicks.
Cant find any burned components near J4801
Any ideas?

J4801 Voltages:
9-10 - 3.43V
14 - 5.16V
21 - 3.30V
23/24/25 - 5.15V
35/36/37/38/39/40/41 - 8.60V

Ordered new trackpad flex cables but any ideas in the mean time?
 

Alan.L

Member
i guess he didn't press "disconnect battery" button before disconnecting the trackpad flex, used a tweezer and shorted PPBUS_G3H_TPAD or other power rails.

check USB data line to see if is shorted, and try a new trackpad.

The power button is working because it doesn't really require a trackpad to function, more like a direct connection using SMC_ONOFF_L.


also, check these fuses on the right:


 
Last edited:

dukefawks

Administrator
Voltages on J4801 without any load connected can be misleading. I bet L4801-4 one of them is fried and now is a resistor. Check them for resistance, should be close to 0 of course.
L4801 being the first suspect as that has always power to it.
 

ajdoc

Member
Thanks Alan and Duke.
L4804 was fried. Replaced and is near 0 Ohms again.

Now got 'dong' sound when connected to charger and nothing else.
No image, no system chime nothing.
Starting to hate this board design...

Any ideas?
 

ajdoc

Member
Did that, works fine when internal screen is unpluged and connected to external screen.
Did a test with connected internal display nothing on the internal - it works on external.
Data on external looks like internal screen has been detected but no image/backlight as when only ext is connected I see logic screen.
When both screens connected I see blurry wallpaper on ext screen.

Any idea? Internal display failed?

BTW. Keyboard and trackpad is working fine with new L4804.
 

Alan.L

Member
try this:

look a the screen cable, there is a conductive foam and there are exposed pins on the connector of the logic board, cover with Kapton tape.





 

Alan.L

Member
I assume you checked the fuse for the screen right, also how did you remove the screen flex cable? you suppose to slide the cable out or slide in. do not use the latch as this will damage the connector.

use a torch and shine a light to the screen to see if you get an image. if doesn't work then you need to buy a damaged screen for testing
 
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