This is probably a unique fix but debug sequence might be useful for future failures.
Got the MBP from a laid off repair tech along with other stuff. Poor repair jobs everywhere I looked. On this board, U3900 appears to be just slightly misaligned from prior reflow/replacement. System fully boots. No camera detected is the issue. Pic from my cheap $15 USB microscope
Checked the camera connector (J4002). Pin 10/11 voltage generated by U3900 was missing so pretty likely camera wasn't putting out the power rails. That left 3 possibilities
- Dead U3900. Since there was prior rework, probably a replacement chip. So perhaps it was good.
- Not getting camera power on signal. The circuit between CPU's request line to U3900 consist of a fuse resistor (R2030) and a pull up/down resistor (R1633) off of 3.3v rail. Both tested good. So the observed misalignment might be the cause.
- No power to the U3900. Since the system booted up fully. S0 rails should all be there.
Didn't really want to do more disassembly (power board, LCD, bluetooth to get a mouse to start the camera app) to take more measurements so opted just to reflow and bump the U3900 so its aligned. And bingo it worked haha. Amazing.
Used an Atten 862-D hot air station. Lots of misinformation on temperature to use with people regularly quoting melting temp of lead/leadfree solder. After watching the video below. I set it to 480C and 85% flow to test remove a couple of BGA DRAM on a dead board to make sure it works well. About 15-20s heat was all it took. Macbook logic board soaked up a lot of heat like a huge heat sink. Air temp probably need to be high enough to combat the heat sink and reasonably fast speed to avoid long term heat on the board.
https://www.youtube.com/watch?v=wYCmU6jMLo8
A lot of people won't quote air temps because so many circumstances (station difference, board size, chip size etc) Make sense, I've killed a couple of old phone boards now haha. Need to learn all the tricks (low melt solder, dealing with underfills, little BGAs on little boards etc)
FYI for future efforts. Probably won't have another misaligned prior work fix again. So check U3900 voltage output at the camera connector. Check 2 resisters on the camera power on circuit are logical starting places.
Got the MBP from a laid off repair tech along with other stuff. Poor repair jobs everywhere I looked. On this board, U3900 appears to be just slightly misaligned from prior reflow/replacement. System fully boots. No camera detected is the issue. Pic from my cheap $15 USB microscope
Checked the camera connector (J4002). Pin 10/11 voltage generated by U3900 was missing so pretty likely camera wasn't putting out the power rails. That left 3 possibilities
- Dead U3900. Since there was prior rework, probably a replacement chip. So perhaps it was good.
- Not getting camera power on signal. The circuit between CPU's request line to U3900 consist of a fuse resistor (R2030) and a pull up/down resistor (R1633) off of 3.3v rail. Both tested good. So the observed misalignment might be the cause.
- No power to the U3900. Since the system booted up fully. S0 rails should all be there.
Didn't really want to do more disassembly (power board, LCD, bluetooth to get a mouse to start the camera app) to take more measurements so opted just to reflow and bump the U3900 so its aligned. And bingo it worked haha. Amazing.
Used an Atten 862-D hot air station. Lots of misinformation on temperature to use with people regularly quoting melting temp of lead/leadfree solder. After watching the video below. I set it to 480C and 85% flow to test remove a couple of BGA DRAM on a dead board to make sure it works well. About 15-20s heat was all it took. Macbook logic board soaked up a lot of heat like a huge heat sink. Air temp probably need to be high enough to combat the heat sink and reasonably fast speed to avoid long term heat on the board.
https://www.youtube.com/watch?v=wYCmU6jMLo8
A lot of people won't quote air temps because so many circumstances (station difference, board size, chip size etc) Make sense, I've killed a couple of old phone boards now haha. Need to learn all the tricks (low melt solder, dealing with underfills, little BGAs on little boards etc)
FYI for future efforts. Probably won't have another misaligned prior work fix again. So check U3900 voltage output at the camera connector. Check 2 resisters on the camera power on circuit are logical starting places.
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