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MacBook Pro A1989 Power Issue.

M

marcosoft360

New member
Hello, I am new here, and want to thank all of you who help us newbies. With that being said, I have a 1989 a customer brought in for repair to his keyboard. Where the connector connects to the board from the keyboard there was corrosion from water damage. Instead of replacing the keyboard, I got a replacement top half. The mac worked before the transfer besides the keyboard. Now, the mac won't turn on. I did not find any shorts, and I unplugged the keyboard and trackpad to see if they were culprit, and also everything else except one side type c connectors. Still nothing. Pressing the power button nothing in all instances. I also connected the mac to another to see if DFU would recognize and it did not. The macbook will not pull charge, there is a fluctuation of 5V 0.5 A, every 3 to 10 seconds. I did check that the 12v rail is steady, but to the right of the screw for the battery, the first inductor which looks to be the largest one on the board (2R7), fluctuates from 0.9v to 4v. Above of the small flex cable next to the battery screw is another inductor (1R0) which measures at 3.38v. I am assuming the 2R7 inductor is connected to the 5v rail.

Any help would be much appreciated to narrow down the culprit.

Thank you
 
M

marcosoft360

New member
Hello, just an update. My helper replaced a logic board for a 1990 today and the mac wouldn't turn on. On both the 89 and 90 he switched the power button and afterwards they were both hard to press. I will look into that tomorrow. However, the 90, I was able to unplug the power button and open the lid and it turned on. I also saw the 5v .5a draw and then immediately switched to 20v .5a/1.2a with the fans spin and shutdown. I tried replicating the solution on the 89 by removing the power button connectors and, it drops 5v .5a to 0v 0.00a when trying to switch to the 20V .5a . This cycle is continuous when plugged in. Just an FYI if you can point me in the right direction. Thank you
 
2informaticos

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

Please, don't mix boards in the thread.

I recommend to inspect for knocked off components, damaged connectors, broken trace.
Such things can happen when the MLB is removed and seated back.

Do you get steady 3V3_G3H_RTC voltage?
Also check at U7800's coils.
If OK, you should check if is detected in DFU mode.

"I am assuming the 2R7 inductor is connected to the 5v rail"
(Partially) wrong assumption.
L7030 is part of buck/boost converter, not directly connected to the input voltage.
Almost never need to check the voltage there.

This MLB must turn on by itself alone on the desk, with (at least) 61W charger.
 
M

marcosoft360

New member
Hello,

Thank you for your response.

I will refrain from mixing boards.

I did check for knocked off components, damaged connectors and broken traces, and saw none.

I did check 3v3_G3H_RTC and get a steady 12v.

I checked the coils at U7800 and L7819 - L7821 no voltage.
L7806 -809, L7813 - L717 has fluctuating voltage from 0v to 1.1v.

I do have a 100w charger that I am using for testing. I confirmed it's working with another Mac.

The only thing I think is important to add, which I don't know is relevant or not, is that the power button was stuck to on for a long time with the battery connected and battery is a t 0V.

I appreciate your time, thank you.
 
2informaticos

2informaticos

Administrator
Staff member
Test the board alone on the desk; keep only USB-C terminal connected.
Check if you get voltage on the big coils.
If board boots, CPU core should drop to 0.65V aprox.

If still not working, then check diode mode to ground on all big coils; including L9080.
 
M

marcosoft360

New member
I have been testing the board alone and only one side usb-c terminal connected.

The only voltages I get are on L7660 3.3v and fluctuating voltage on L7030 from 1.v to 4.1v.

I have tested the coils in diode mode and this is what I get: .351v (L9080), others: .514v, .496v, .897v, 0.137v (L8102). 19.50 ohms (L7702), 3.8ohms (L7270), 3.8ohms (L7220), 3.8ohms (L7210), .800 ohms (L7410), .600 ohms (L742), .800 ohms (L7430)

Let me know if you need me to check anything else out. I am now wondering how my helper tried DFU without the power button working. Is this possible to set the mode without the power button working properly? If nothing looks wrong do you think I should try resetting anything with keyboard commands and anything I should try now that the power button is fixed?

Thank you for your time, much appreciated.
 
M

marcosoft360

New member
No go with the DFU after fixing the button.

Going through some threads I saw one regarding the CD3215C and the 1V1_LDO. Three of the CD3215C have a fixed 1.15v and the forth fluctuates from 0-1v. Diode mode shows the 3 that are static at 3v to 2v, the one that fluctuates is at 1V drops. However, I am testing pin 35 on the CD3215C bc it's the only one that shows 1V1. It is labeled PP1V1_UPC_XB_LDO_BMC

Is this correct and can you let me know if I am checking the correct output.
 
M

marcosoft360

New member
Swapped the CD3215 that was fluctuating at LDO and same thing. However, following a boot up sequence at the same location where I swapped the CD3215, I measured the PPDCIN_G3H and it's showing 3.92v instead of 5v like the rest. Can the issue be the Q3100 instead of the CD3215?
 
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