Hi,
I have a 2012 MacBook Pro in great cosmetic shape that I just acquired and am working on. Logic Board is 820-3330. No signs of water damage. Appears to be good battery.
Initial symptom was it wouldn't boot reliably. Once in a while it would successfully boot to desktop with no display issues but shutdown shortly thereafter. Sometimes it would start booting and progress bar would advance very slowly and never complete. System had green light on charger and slow fan spin. No chime or mouse LED when it doesn't boot.
SMC reset seemed to work (LED on charger changed color). These occasions usually occurred when the system was first powered on after being off overnight and then only once until off overnight again.
I noticed board getting hot on side opposite U1800 PCH.
Then, while trouble shooting (I believe I was probing around U7400 pins 27 and 28 at the time but that may be a coincidence), things got worse. Lost green light on charger.
Had to change R7005 (20K) which brought back green light but still had no PPBUS_G3_Hot. Replaced U7000 and Q7030 and Q7035. However, instead of 0.46V (diode mode) on Q7030 pins 1,2,3 and Q7030 pin 5, I only get .001 V. Resistance on this line is 1.2 ohms to ground. Removed U7000 and still got same readings. Replaced again and same readings.
Fuses on that line are good.
Looked at all places this signal goes and can't identify any obvious shorts to ground. Reluctant to power the card on given these readings.
Even if I solve this new problem, I still have the original problem to work out.
I am beginning to suspect the board is not repairable (could U1800 have gone bad?) and I may need to sell the unit for parts.
Suggestions?
I have a 2012 MacBook Pro in great cosmetic shape that I just acquired and am working on. Logic Board is 820-3330. No signs of water damage. Appears to be good battery.
Initial symptom was it wouldn't boot reliably. Once in a while it would successfully boot to desktop with no display issues but shutdown shortly thereafter. Sometimes it would start booting and progress bar would advance very slowly and never complete. System had green light on charger and slow fan spin. No chime or mouse LED when it doesn't boot.
SMC reset seemed to work (LED on charger changed color). These occasions usually occurred when the system was first powered on after being off overnight and then only once until off overnight again.
I noticed board getting hot on side opposite U1800 PCH.
Then, while trouble shooting (I believe I was probing around U7400 pins 27 and 28 at the time but that may be a coincidence), things got worse. Lost green light on charger.
Had to change R7005 (20K) which brought back green light but still had no PPBUS_G3_Hot. Replaced U7000 and Q7030 and Q7035. However, instead of 0.46V (diode mode) on Q7030 pins 1,2,3 and Q7030 pin 5, I only get .001 V. Resistance on this line is 1.2 ohms to ground. Removed U7000 and still got same readings. Replaced again and same readings.
Fuses on that line are good.
Looked at all places this signal goes and can't identify any obvious shorts to ground. Reluctant to power the card on given these readings.
Even if I solve this new problem, I still have the original problem to work out.
I am beginning to suspect the board is not repairable (could U1800 have gone bad?) and I may need to sell the unit for parts.
Suggestions?
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