820-3432 no lcd

oneoone

New member
It appear I need to replace c8312 as I am getting no voltage from it and it looks a bit ugly. However in an attempt to replace it I have misplaced the little bugger on my trash board, how would I go about finding equivalent caps on the trash board I have? Or would I need to buy a new trash board from aliexpress.

Thanks.

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oneoone

New member
Thanks for the promp reply Duke.
820-3432 is the name of the brd file on the mid 2013 macbook air. I don't know what it is either. So the c8312 chip is not required and I should remove it instead of replacing it?
 

oneoone

New member
U8300 pins 2&3 are 3.3v; nothing on pins 4 & 5
C8309 is 3.3v
C8311 is 0
C8312 is removed

I have replaced U8300 and still getting the same results

Any ideas what to test next?

Thanks in advance
 

oneoone

New member
So before I took it apart it had chime and green light.
Now no chime and no green light :(

I took the following measurements from U7090:

1) 0.58
2) 0.1
3) 128.33
4) 127
5)gnd
6) 17.77
7)NC
8) 17.77

Pin 4 was shorting to ground. Replaced U7090, and tested it for shots to ground before powering it on. Now after powering it on the I am getting a short to ground on pin 4.

The numbers I am getting are obviously so far wrong I don't know what to do. This is my first board I have tried to fix so please don't abuse me too much duke... :)

ORtCOku.jpg
 
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oneoone

New member
3v42 reads 0.1v. Testing in continuity mode suguests it is shorted to ground. Is this where I should be focusing my research?

EDIT: I am about to remove L7095 and test for a short either side as per Louis instructions here: How does PP3V42_G3H circuit work and does it require PPBUS_G3H to operate?

EDIT2: short to ground still exists on bottom pad. Are there any tips to finding what is shorting it to ground or should i just start pulling up everything one by one until the short is gone?
 
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dukefawks

Administrator
Inject voltage and see what heats up, start low at 1V and see how much current it draws and go up from there. You fried this board.....
 

oneoone

New member
I 100% fried the board. Is it salvageable? Where is the best place to learn how to not fry boards or is it just experience?
 

oneoone

New member
I also don't have a working power meter, so looks like I am going on a bit of an expedition unless you have a solution?

Thanks
 

oneoone

New member
merry xmas duke.

I bought a power supply, don't really know how to use it. What would be the best points to inject voltage to?
 

dukefawks

Administrator
On the shorted rail, easiest at the coil. Start with low voltage and never go over the normal voltage that is normally on the rail. Observer the current, 2-3 amps should heat something up.
 

oneoone

New member
what does it mean if i don't have 3.42 but it doesn't appear to be shorted to ground?

it would only let me put in .05 amps
 
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