Hi All.
I have a very strange issue that I have been trying to fix for a few days now.
Model: MacBook Pro A1278
Logic board: 820-3115-B
Laptop history:
No visible liquid damage/corrosion, but found evidence of other rework (flux) so any signs of liquid may have been cleaned. The laptop went in for a battery replacement but wasn't working afterwards and was deemed unfixable (as told to me by previous owner). Not sure if this was by Apple, or another repair company. The flux found was found around ISL6259HRTZ, so can assume it was replaced at some stage. Also there is one missing pin in one of the memory slots. Looks like it snapped at some stage. The remains of this broken off pin removed by me, so not shorting anywhere.
The issue:
- No boot at all while on charger or battery
- No charger light at all
- 10mA constant current draw from power supply
- ADAPTER_SENSE line is 0v, but not shorted to ground
- SMC_BC_ACOK(CHGR_ACOK) is short to ground, but only when the board is powered (by either adapter or battery)
- PPBUS_G3H fluctuates between 0v and 3v when connected to charger, but voltage drops steadily while measuring towards 0v
- PPBUS_G3H shows 12.33v when connected to a charged functional battery (but SMC_BC_ACOK still shows as short to ground, and still no boot or fan spin)
- Most of the S5 rails not present - due to missing PPBUS_G3H I guess
- PP3V42_G3H is present and measures 3.45v
What I have tried:
I have tried a known working DC in board with the exact same results.
I have replaced the following components with no noticeable changes:
- U7000 (ISL6258) - Replaced 3 or 4 times, so no chance all of these were faulty
- Q7510, Q7520
- U6900
- Checked for shorted caps and bad resistors on the SMC_BC_ACOK line asper touch points indicated by Boardview
I Have removed the following components in an attempt to get rid of the SMC_BC_ACOK short with no results. (I can't replace these as I am waiting for replacement parts to arrive)
- Q7030, Q7035
- U4900 (SMC)
- Q6901
Until I can figure out why there is no voltage showing on ADAPTER_SENSE I am pretty sure I will not be able to get PPBUS_G3H back either. Really baffling me at the moment, and hoping there is something obvious that I am missing? Could there be some sort of short inside the board that only shows up when powered?
Any and all help appreciated!
Thanks.
I have a very strange issue that I have been trying to fix for a few days now.
Model: MacBook Pro A1278
Logic board: 820-3115-B
Laptop history:
No visible liquid damage/corrosion, but found evidence of other rework (flux) so any signs of liquid may have been cleaned. The laptop went in for a battery replacement but wasn't working afterwards and was deemed unfixable (as told to me by previous owner). Not sure if this was by Apple, or another repair company. The flux found was found around ISL6259HRTZ, so can assume it was replaced at some stage. Also there is one missing pin in one of the memory slots. Looks like it snapped at some stage. The remains of this broken off pin removed by me, so not shorting anywhere.
The issue:
- No boot at all while on charger or battery
- No charger light at all
- 10mA constant current draw from power supply
- ADAPTER_SENSE line is 0v, but not shorted to ground
- SMC_BC_ACOK(CHGR_ACOK) is short to ground, but only when the board is powered (by either adapter or battery)
- PPBUS_G3H fluctuates between 0v and 3v when connected to charger, but voltage drops steadily while measuring towards 0v
- PPBUS_G3H shows 12.33v when connected to a charged functional battery (but SMC_BC_ACOK still shows as short to ground, and still no boot or fan spin)
- Most of the S5 rails not present - due to missing PPBUS_G3H I guess
- PP3V42_G3H is present and measures 3.45v
What I have tried:
I have tried a known working DC in board with the exact same results.
I have replaced the following components with no noticeable changes:
- U7000 (ISL6258) - Replaced 3 or 4 times, so no chance all of these were faulty
- Q7510, Q7520
- U6900
- Checked for shorted caps and bad resistors on the SMC_BC_ACOK line asper touch points indicated by Boardview
I Have removed the following components in an attempt to get rid of the SMC_BC_ACOK short with no results. (I can't replace these as I am waiting for replacement parts to arrive)
- Q7030, Q7035
- U4900 (SMC)
- Q6901
Until I can figure out why there is no voltage showing on ADAPTER_SENSE I am pretty sure I will not be able to get PPBUS_G3H back either. Really baffling me at the moment, and hoping there is something obvious that I am missing? Could there be some sort of short inside the board that only shows up when powered?
Any and all help appreciated!
Thanks.
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