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[SOLVED]820-2936-A no power

K

Kalemaroni

Member
Hi all, I am new to board level repair but working hard on the learning curve and would like to give many thanks to Louis for his videos.

I bought an 820-2936-A board and had green + orange light with magsafe and battery plugged in. I then decided to write down some values of U7000 to cross reference with another board I was working on but I think I shorted pins 2+3 and now I get no light at all! I have since been made aware of the existence of, and that I should've used, the test points to measure voltage not the actual pins so as not to cause the damage that I most likely have caused! In the meantime I'd be very grateful for some assistance in recovering this board.

Some measurements that may prove helpful in assisting me:

R6929 0v
C6908 3.4v
U6901 3.4v on PP3V42_G3H but 0v on all other pins.
U7000 DCIN (pin 2) 16.4v
U7000 ACIN (pin 3) 0v
​​​​​​​
Many thanks in advance for any responses.
 
K

Kalemaroni

Member
So I swapped the ISL out and got a green light but no orange. I was getting 0v on the bottom pins (15-21) so I tried re-positioning the ISL and then it went from bad to worse. I tried another ISL and same results.

Here are current readings and pictures of the area:

U7000
pin 1 15.6v
pin 2 seems to go up and down between 0.065v and 0.075v. Sometimes when I measure it after not having touched it for a period it starts at around 1 something volts and drops quickly before continuing the aforementioned pattern.
pin 3 3.98v
pin 4 3.45v
pin 5 0v
pin 6 3.45v
pin 7 0v
pin 8 0.39v
pin 9 0.04v
pin 10 0.379v
pin 11 3.45v
pin 12 3.45v
pin 13 3.42v
pin 14 0v
pin 15 0v
pin 16 starts at about 0.24v and drops quickly to 0v
pin 17 0.092v
pin 18 0.09v
pin 19 0.005v
pin 20 0.005v
pin 21 0v
pin 23 0.085v
pin 24 0.085v
pin 25 0.003v
pins 26, 27 & 28 start at around 12.5v and drop slowly at a rate of around 0.005v a second.
 

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A

aprendiz

Moderator
Seems is not soldered properly, pin 2 was 16.4V before you replace the ic, redo the soldering job and check value for R7005....
 
K

Kalemaroni

Member
I have tried 4-5 different ISLs now, I've cleaned up the pads and re-tinned each time and I'm getting the same results - very frustrating! I'm getting a green light at least now but still pins 1, 15-21 and 26-28 are reporting bad values.

I don't know if maybe I'm not doing it right or if the chips are bad - I don't have the experience to tell. I have watched numerous videos on the process, I have tried letting the chip just fall into place as the solder melts, I've tried pushing it down firm, and I've tried letting the tweezers rest with just a little pressure but same results each time. I've cleaned up the joints with flux and solder afterwards and checked as much as I can that there are no bridges.

Is there something else that could be causing the problems or do I just need to get this chip on right? Is it possible I've burnt something out on the board and is there a way to check for this if so?
 
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