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[SOLVED]820-3115 No Boot

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cainrand

New member
I have a Macbook (820-3115) that came in "dead" and the customer states that a "whole bottle of water is in there."

It does not turn on, no chimes, no fan, nothing.
Battery LED meter on the side shows the battery at about 50%.
MagSafe gives me a green light but never changes to orange (always green).

Up until now the extent of my diagnostic skills have been limited to obvious things - in this case I would have thought there would be obvious water damage on the board.
There is no apparent water damage on the board. The only bit of green-rust/oxide build up that I could find was very small amount on C5856 cap near the key board light connector which really was not a problem at all.

I have read through the Beginners presentation power point and tried to check some things based on what I read there but the truth is, I don't yet know exactly what I am doing and I think I am just chasing a rabbit I will never catch without some guidance here.
I can tell you there is power in various places... initially I thought maybe a water spill caused some problems with the keyboard and power switch so I tried turning it on using the Power On pads (there is 3.45V on one pad) but it does not turn on.

I have the board out of the laptop and would appreciate any help I can get on where should I really start?
I should add... I do not have a working board to compare with.
 
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aprendiz

Moderator
Get the schematic and boardview and tell me what voltage do you have on PPBUS_G3H, SMBUS_BATT_SCL and SMBUS_BATT_SDA with and without battery connected, charger always connected ofcourse...
 
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cainrand

New member
PPBUS_G3H
With Batt, V=12.58
Without Batt, V= 12.58

SMBUS_BATT_SCL
With Batt, V= 3.45 (not steady, (fluctuation) drops down to 3.2 but mostly is at 3.4)
Without Batt, V= 3.45 (not steady, (fluctuation) drops down to 3.2 but mostly is at 3.4)

SMBUS_BATT_SDA
With Batt, V= 3.45 (not steady, (fluctuation) drops down to 3.2 but mostly is at 3.4)
Without Batt, V= 3.45 (not steady, (fluctuation) drops down to 3.2 but mostly is at 3.4)
 
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aprendiz

Moderator
PP3v3_S5 is not stable at 3.3V?? if yes maybe you have a short on 5V rail........

If PP3V3_S5 is stable, check U2600 for corrosion, check if PPVRTC_G3_OUT is present and if SYSCLK_CLK32K_RTC is present...
 
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cainrand

New member
Resistance to GND on 3V3_S5? = Diode mode says .142

S5_PWRGD pulsing too? = Yes, pulsing when magsafe connected, not pulsing on battery only.
 
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cainrand

New member
I will take a look at those tomorrow.

What do you think of buck converter U7200 being an issue? There is slight evidence that water was around this chip (rust like discoloration) and I am wondering if it caused some problems within.

I ordered some chips and figured I could change it anyway which brings me to the next question... I have never removed a buck converter. I see it has a ground solder underneath but I am wondering if there is any type of adhesive as well. Are there any tips for removing this?
Thanks


Edit: I just now realized that TPS51125 is the U7200 buck!
 
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cainrand

New member
So I was looking at TPS51125

I have a steady 12V coming in on pin 16 but I have a pulsing 3.3V out on pin 8 and a pulsing 5v out on pin 17.
 
C

cainrand

New member
Finally got some parts in.
Replaced the buck converter and tested - voltage is now steady and not pulsing.

System is charging. Laptop boots and appears to be working as it should!

Thank you for all the help!!
 
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