This is my first post, I would really appreciate some help to resolve a logic board fault.
Product details: MBP, A1278, Mid 2012, Logic Board Part # 820-3115-B
Fault: Does not power on, no chime, fan, display etc. I may have shorted the display connector onto the logic board when replacing the lcd panel, which was replaced after being damaged by impact.
I am unsure for certain if this is the case, however I had the battery connected while replacing the lcd panel (mistake), and I think I saw a spark between the disconnected display connector and the logic board. I have examined the logic board thoroughly but cannot see evidence of this. However, the MBP was operational prior to replacing the LCD.
The magsafe led is green when connected.
What I have done so far:
1. Metered magsafe voltages, DC 17.1v pin 2, DC 3.41v pin 3.
2. Metered DC 3.41v between keyboard bypass pad and ground.
3. Attempted SMC bypass sequence detailed in other posts - same result
4. Removed everything (RAM, all peripheral connectors, battery) except fan, speaker and magsafe connector from logic board. Short keyboard bypass pads. Same result.
5. Tested everything I think could be fuses - white ceramic devices both sides of the board, and a device labeled P close to display connector. All test short circuit.
I haven't been able to locate a schematic for this MB, although I have obtained one for earlier models.
Any assistance you can offer to help me troubleshoot this problem would be appreciated.
Note: Because I am a new user, I am unable to send PM's until I have at least 5 posts and been active more than 1 day.
Update: I have since discovered a component which appears to be blown. It meters 0.03 ohms, pretty much a short circuit. I suspect it is some sort of choke. Can anyone assist me to identify this component so I can source a replacement?
Cheers
Steve
Product details: MBP, A1278, Mid 2012, Logic Board Part # 820-3115-B
Fault: Does not power on, no chime, fan, display etc. I may have shorted the display connector onto the logic board when replacing the lcd panel, which was replaced after being damaged by impact.
I am unsure for certain if this is the case, however I had the battery connected while replacing the lcd panel (mistake), and I think I saw a spark between the disconnected display connector and the logic board. I have examined the logic board thoroughly but cannot see evidence of this. However, the MBP was operational prior to replacing the LCD.
The magsafe led is green when connected.
What I have done so far:
1. Metered magsafe voltages, DC 17.1v pin 2, DC 3.41v pin 3.
2. Metered DC 3.41v between keyboard bypass pad and ground.
3. Attempted SMC bypass sequence detailed in other posts - same result
4. Removed everything (RAM, all peripheral connectors, battery) except fan, speaker and magsafe connector from logic board. Short keyboard bypass pads. Same result.
5. Tested everything I think could be fuses - white ceramic devices both sides of the board, and a device labeled P close to display connector. All test short circuit.
I haven't been able to locate a schematic for this MB, although I have obtained one for earlier models.
Any assistance you can offer to help me troubleshoot this problem would be appreciated.
Note: Because I am a new user, I am unable to send PM's until I have at least 5 posts and been active more than 1 day.
Update: I have since discovered a component which appears to be blown. It meters 0.03 ohms, pretty much a short circuit. I suspect it is some sort of choke. Can anyone assist me to identify this component so I can source a replacement?
Cheers
Steve
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