Hi,
stubborn board again. So I got it with not turning on problem. No liquid damage, but had replaced backlight IC before, the rest looks good. There is green and orange light on MagSafe, but fan doesn’t spin, just try to start and stops (Quarter fan spin). PPBUS_G3H ~4v, not shorted. I‘ve checked the area of U7000 (ISL6259) and adapter current sensing resistors R7021/22 were blown (resistance in kohm, the battery side was measuring 2,2ohm). I’ve replaced them along with ISL, resistance between R7021/22 got 20ohm. After connecting adapter had no fan spin though PPBUS raised to 8,56v. It turned out, that adapter resistors blew again, so I’ve replaced ISL and resistors again. This time board started, so I decided to put it in topcase and test it. Another adapter connection blew the resistors again, PPBUS dropped to ~4v... I’ve checked all components on page 53 of schematic... R7005 measures 20ohm, R7020 and R7050 are ok, C7020 is ok... I’ve replaced all set again and tried with battery only - no reaction. I’ve tried with different MagSafe boards and I/O cables - it keeps burning these resistors and ISL... I’ve also checked voltage rails for shorts and haven’t found any... just because board started after one of ISL/resistors replacement I believe power rails are not the actual problem here. Do you have any suggestions?
stubborn board again. So I got it with not turning on problem. No liquid damage, but had replaced backlight IC before, the rest looks good. There is green and orange light on MagSafe, but fan doesn’t spin, just try to start and stops (Quarter fan spin). PPBUS_G3H ~4v, not shorted. I‘ve checked the area of U7000 (ISL6259) and adapter current sensing resistors R7021/22 were blown (resistance in kohm, the battery side was measuring 2,2ohm). I’ve replaced them along with ISL, resistance between R7021/22 got 20ohm. After connecting adapter had no fan spin though PPBUS raised to 8,56v. It turned out, that adapter resistors blew again, so I’ve replaced ISL and resistors again. This time board started, so I decided to put it in topcase and test it. Another adapter connection blew the resistors again, PPBUS dropped to ~4v... I’ve checked all components on page 53 of schematic... R7005 measures 20ohm, R7020 and R7050 are ok, C7020 is ok... I’ve replaced all set again and tried with battery only - no reaction. I’ve tried with different MagSafe boards and I/O cables - it keeps burning these resistors and ISL... I’ve also checked voltage rails for shorts and haven’t found any... just because board started after one of ISL/resistors replacement I believe power rails are not the actual problem here. Do you have any suggestions?
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