Macbook Pro A1502 (820-4924-A) beeping, no signs of water damage.

[agavrilescu]

Hi guys, I am hoping someone can help. I have purchased a very cheap Aand faulty macbook pro A1502 (820-4924-A) to play with and learn a little about repairs.

Now, the laptop is in great condition internal and external, doesn't seem to have been messed with, however, when plugged in and power button is pressed it starts to chime, continuous 3 chimes.

I opened the computer and checked the motherboard. I can see on the inside of the motherboard, around U7700 chip (back-light chip?) there was something that caused a short as the interior of the case is melted (see photo).

The problem is I dont see any obvious damage on the motherboard itself, as you can see in the second image, everything looks quite ok.

I understand it can be a problem with RAM and CPU, however I would like to exclude anything else before trying to reflow the RAM.

I have the schematics and board view but I dont know if there is actually a way to test the RAM and CPU. I have done some measurements that to be honest I dont know if I measured the right things.

PPBUS_G3H = 12.56 V
PBUS_S0_VSENSE (Q5480 pin 3) = 3.40 V
PPVCC_S0_CPU = 1.865 V
PPVTTDDR_S3 = 0.60 V
PP0V6_S0_DDRVTT = 0.273 V

L7430 = 1.205v



Thanks to anyone who can help!

Alex

[MobileXT]

Re: Macbook Pro A1502 (820-4924-A) beeping, no signs of water damage.

check the voltage of the RAM if present. If present then reflow all the RAM chips.